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ANL/APS/TM--8

ARGONNE NATIONAL LABORATORY DE91 0077949700 South Cass Avenue

Argonne, Illinois60439

ANL/APSfrM-8

ATOMIC PHYSICS AT THE ADVANCED PHOTON SOURCE:WORKSHOP REPORT

Proceedings of a workshop held at

Argonne National LaboratoryMarch 29-30, ].990

Workshop Co-Chairs:

H. Gordon BerryYoshiro Azuma

Noura Berrah Mansour

October 1990

work sponsored by

U.S. DEPARTMENT OF ENERGY

Omce of Energy Research _A_TER tb

CONTENTS

Page

ACKNOWLEDGMENTS ............................................................................. v

ABSTRACT .............................................................................................. 1

COMMENTS: APS WORKSHOP ON ATOMIC PHYSICSAlan Schriesheim, Director, Argonne National Laboratory ....................... 3

PRESENTED PAPERS ............................................................................... 5

Status Report on the Advanced Photon Source, Spring 1990David E. Moncton .................................................................................. 7

Opportunities for Atomic Physics with Hard Synchrotron RadiationBernd Crasemann .............................................................................. 12

New Frontiers in X-Ray Photoionization of Ions and AtomsSteven T. Manson ................................................................................ 38

The Advanced Light Source: A New 1.5-GEV Synchrotron RadiationFacility at the Lawrence Berkeley Laboratory

Alfred S. Schlachter ............................................................................ 59

The RIKEN - JAERI 8-GEV Synchrotron Radiation Project - SPring - 8Yohko Awaya .................................................................................... 123

Photoionization of Ions and the General Program in Atomic and MolecularPhysics at Daresbury

John B. West ..................................................................................... 144

Research with Stored Multi-Charged Ions at the APS and the NSLSDavid A. Church ............................................................................... 148

Thoughts on Future ESSR Studies of Inner Core LevelsManfred O. Krause ............................................................................ 183

Beam-Line Considerations for Experiments with Highly-Charged Ions1 Brant M. Johnson ............................................................................... 200

Spectral Characteristics of Insertion Device Sources at the AdvancedPhoton Source

P. James Viccaro ................................................................................ 227

!

iii

CONTENTS (Cont'd)

Can a Powerfill Source (APS) Cast Useful Light on Atomic Hole StateProcesses?

Paul L. Cowan ................................................................................... 272i

Studies of Free and Deposited Clusters Using Syachrotron RadiationWolfgang Eberhardt ........................................................................... 290

Atomic Physic_ with New Synchrotron Radiation: Report from theJapanese Working Group

Masahiro Kimura. .......................... 298

Argon - Ion Charge Distributions Following Near - Threshold IonizationJ on C. Levin ....................................................................................... 318

Nuclear Bragg Diffraction of' Synchrotron X-RaysJohn Arthur. 350

Revealing Inner Shell Dynamics with Inelastic X-Ray ScatteringCarl Franck ................................................................................... 370

CLOSING REMARKSIvan Sellin. ....................................................................................... ;_9

PROGRAM ............................................................................................ 403

WORKSHOP PROGRAM AND ORGANIZING COMMITTEE ..................... 408

PARTICIPANTS .................................................................................... 409

iv

ACKNOWLEDGMENTS

The Workshop on Atomic Physics at the Advanced Photon Source was jointlysponsored by the Physics Division, the Advanced Photon Source, and the Divisionof Educational Programs at Argonne National Laboratory. The workshoporganizers wish to express their thanks to the sponsors for making this meetingpossible, and to ali invited speakers for sharing their research interests and theirinsights. [['hanks also go to Bonnie Meyer and Susan Pi_ 'loglou of the AdvancedPhoton Source and Joan Brunsvold of the Office of Public Affairs for their valuableassistance.

Program and Organiz, ing Committee

WORKSHOP ON ATOMIC PHYSICS AT THE ADVANCED PHOTON SOURCE

ABSTRACT

The first Workshop on Atomic Physics at the Advanced Photon Source was held atArgonne National Laboratory on March 29-30, 1990. The unprecedentedbrightness of the Advanced Photon Source (APS) in the hard X..ray region isexpected to make possible a vast array of new research opportunities for theatomic physics community. Starting with discussions of the history and currentstatus of the field, presentations were made on various future directions tbrresearch with hard X-rays interacting with atoms, ions, clusters, and solids.Also important were the discussions on the design and status of the four next-generation rings coming on line during the 1990's: the ALS 1.6-GEV ring atBerleley; the ESRF 6.0-GEV ring at Grenoble (1993); the APS 7.0-GEV ring atArgonne (1995); and the SPring-8 8.0-GEV ring in Japan (1998). The participationof more than one hundred scientists from domestic as well as foreign institutionsdemonstrated a strong interest in this field. We plan to organize follow-upworkshops in the future emphasizing specific research topics.

H. Gordon BerryYoshiro AzumaNoura Ber'rah Mansour

Alan Schriesheim COMMENTS:APS WORKSHOP ON ATOMIC PHYSICS

March 29, 1990

Ladies and Gentlemen, it is a pleasure to welcome you to Argonne NationalLaboratory and to this workshop on the ways that synchrotron radiationgenerally, and the Advanced Photon Source (APS) specifically, carl advanceatomic physics.

We are pleased to see you here for a variety of reasons. For one thing, wewant you to know all that we are doing to get the APS ready for your use. Foranother, we welcome the chance to learn from the leading researchers in the fieldwhat you are doing in this area of science.

Most of all, we want to be sure that all of us are prepared to utilize fully theAPS as a vital new tool. The combination of high intensity and high-energy x-raysprovides unique opportunities in atomic physics, particularly in studying theprocesses that follow deep-inner-shell electron dislocation.

First, let me tell you about our progress. Many of the current developmentsthat will affect the future of the APS are in a peculiar corner of science known as"political" science.

We are receiving $51,5 million for APS construction and supportingoperations this year. We expect to break ground about a month from now.

The Department of Energy's spending plan, which is reflected in President: Bush's 1991 budget proposal to Congress, supports construction which would

_llow us to start research in the fall of 1995. Some members of Congress feel thatwe can optimize the nation's financial investment by shortening that constructionschedule.

This would require $120 million in APS funding for 1991 instead of the $75= million in President Bush's proposed budget to Congress. I've discussed this

accelerated schedule with Secretary of Energy James Watkins. He has indicatedto me privately and to Congressional hearings that he would welcomeincremental funding for such a purpose.

We are ready to accelerate this project. We have been hiring staff as fast asfimds are released to us for that purpose. Currently there are 165 Argonne peoplein the APS orgamzation.

The cultural, archeological, geological, and soil work on the constructionsite is either on schedule or completed. The study which found no significantenvironmental impact has been approved by the state Department of Energy andis moving forward toward approval by the federal DOE.=

',qNI_ ni

Both the architect-engineering contract and the construction managementcontract have been signed with leading national firms.

The first quadrupole magnet to focus the positron beam has been shipped tc_Fermilab for testing. The prototype undulator which will wiggle the positronbeam in order to generate brilliant x-rays has been designed by APS for testing atBrookhaven National Laboratory.

Testing continues on the aluminum vacuum chamber prototype. And weare advancing development of a unique design to run liquid gallium throughchannels in the silicon crystals that act as polarizing mirrors for the x-ray bearn,both to cool one side of the crystal and to heat the opposite side to offset distortion.

In collaboration with researchers at the University of Michigan _ndAT&T's Bell Laboratory, we have developed a charge-coupled device to makeultra-fast x-ray diffraction images of materials under stress.

We are also preparing our staff to make this the most user friendly facilityever built in the United States. And I don't mean just the APS Staff.

With 200 research programs, Argonne probably can claim the mostdiversified mix of disciplines and expertise of any national laboratory. We believethat diversity represents an advantage for both this Laboratory and for the users of'APS.

It offers you a smorgasbord ofcollaboratioll and assistance ranging fromtheorists and experimentalists through advanced computer specialists,accelerator engineers, and technicians.

It is our goal to have each user of APS spend the maximum amount of thetime at Argonne on the experiment. We expect to apply what _e have learned inthe operation of our other accelerators -- like the Intense Pulsed Neutron Sourceand ATLAS -- to save the user time on setting up, operation of the facility,collection of data, and bureaucracy.

That is why it is important for us to have you here for thi_ workshop and tolearn what you foresee as your needs when we start generating the most brilliantx-rays in the world. Thank you again for coming to this conference and for yourcontinuing interest in the Advanced Photon Source.

PRESENTED PAPERS

'_' _11' _M',,lrjl,'_ll"'lNIl_llH_l"r_,, "rl..... _ '" Ii ......

STATUS REPORT ON THE ADVANCED PHOTON SOURCE, SPRING 1990

by

David E. Moncton

Associate Laboratory Director, Advanced Photon SourceArgonne National Laboratory

INTRODUCTION

The Advanced Photon Source (APS) at Argonne National Laboratory has beendesigned as a national user facility for synchrotron-radiation lesearchers fromindustry, universities, and national laboratories. In fact, the APS user communityhas been an important source of guidance and expertise throughout the p_'oject'splanning cycle.

By providing x-ray beams more brilliant than those currently available, the APSpromises to play a substantial role in anydiscipline where knowledge of thestructure of matter is important, from basic research in materials and chemistry tocondensed-matter physics, biology, and medical applications. The science now inprogress at existing synchrotron-radiation facilities, and the science being proposedfor the APS, underlie virtually all modern technologies.

In February of 1986, a conceptual design report (CDR) was issued detailing plansfor a next-generation synchrotron-radiation machine, the 6-GEV Synchrotron X-raySource. In April of 1987, a second CDR formalized the design of the 7-GEVAdvanced Photon Source. That design has been refined and carried forward to itscurrent level of construction readiness. On the eve of ground-breaking ceremonies,a review of APS status is appropriate.

APS FACILITY OVERVIEW

The APS facility is to be constructed in the southwest corner of the Argonne siteon a 79-acre parcel of land with very good geological characteristics.

The experimental hall will be 390 meters in diameter, with the storage ringnearest the inner wall of the large hall. The linac, positron accumulator ring, andbooster are to be located in the infield. Lab/office modules for users will be located

around the perimeter of the ring. Staff and long-term visitors will occupy an officebuilding situated olltside the ring. The APS will provide research opportunities forseveral thousand scientists in total, with 300 to 400 taking data at any one time.

The 58-m-long, 60-Hz APS linac will initially accelerate electrons to 200 MeV.One-third of the way down the linac, the electrons will impact on a tungstenpositron-conversion target. Positrons will be captured and accelerated to 450 MeVover the remaining two-thirds of the linac and then injected into a smallaccumulator ring, approximately 31 meters in circumference, where successive 450-MeV pulses from the linac will be stacked. The accumulator ring serves twofunctions: to damp the positron emittance, thereby making the beam more compact,and to accumulate 24 pulses from the linac while the booster is ramping-up the

previous set of pulses. After injection into the 368-m-circumference booster,positrons will be ramped-up from 450 MeV to 7 GeV in one-quarter of a second.Because it cycles back down to 450 MeV in order to pick up the next pulse, thebooster performs two cycles per second, making it a 2-Hz machine.

The storage ring, 1104 meters in circumference, is designed for a nominal energyof 7 GeV. All calculations of undulator spectra indicate an optimal energy rangebetween 7 and 7.5 GeV. At higher energies, the performance of undulators in theprincipal x-ray range, where APS will operate, begins to ,--leteriorate, making 8, 9, o1"10 GeV problematic in terms of usefulness. Under normal operating conditions,about 30 of the 1296 available rf buckets will be filled with positron bunches, each

carrying on the order of 5 milliamps. Anticipated filling time is one minute.The APS storage ring will have 40 sectors that each include a straight section.

Each sector will contain one insertion-device (ID) beamline and two bending

magnets. One of the two bending magnets in each sectorwill be available to extractradiation; thus, a sector from the user's point of view is an insertion device and itscompanion bending-magnet beamline. Allowing for rf cavities and injectionapparatus, there will be 34 sectors available to user groups.

APS undulators will produce x-ray beams withspectral brilliance in the rangebetween ! 018 and 1019 photons/s/0.1%BW/mrad2/mm 2. That brilliance represents anincrease of 3 or 4 orders of magnitude over what is now available from, for instance,bending magnets at the National Synchrotron Light Source. There are other deviceswhich perform in the intermediate range, but nothing extant in the U.S., or in factthe world, is capable, certainly on a dedicated basis, of producing brilliance at thelevel to be achieved by the APS.

Space for users at existing synchrotron-radiation facilities has historically been inshort supply. The APS design calls for one user module, containing two labs andcomplementary offices, for each sector of the machine, providing a significantimprovement in the quality of life for the research community around the ring.

RESEARCH AND DEVELOPMENT HIGHHGHTS

Insertion devices

A collaboration between the APS Experimental Facilities Division (EFD) and re-searchers at Cornell University resulted in the design of a new insertion device, theAPS/CHESS undulator. APS staff then worked with Spectra Technology ofBellevue, Washington, to construct the lD, and in 1988 the prototype APS/CHESSundulator was installed at the Cornell Electron Storage Ring, where it performedextremely well.

A prototype ultraviolet undulator has now been constructed and it will soon betested in the vacuum ultraviolet ring at Brookhaven National Laboratory. Currentlyunder consideration is a device to produce circularly polarized radiation, an advancecertain to be of interest in the atomic physics community.

OpticsThe problem of thermal loading on beamline optical components is also the

subject of an EFD study. When an intense x-ray beam strikes a monochromating

crystal or a mirrored surface, that surface is heated, causing a distortion, or localthermal bump. These high power densities, which will occur at unprecedentedlevels at the APS, would be disastrous to a beam's optical quality. A multi-stepprocedure developed by APS staff will model the effect of localized high heat loadson optics. Using the Cornell machine and beams from the prototype APS/CHESSundulator, _he resu!ts of th.ese calculations have been intercompared withperformance to determine the reliability of ,'he finite--element..analysis approach andto optimize schemes for optics cooling adequate to the needs of APS.

While the state of the art in optics cooling has been to run water through_-ha'anels close to the surface of a crystal, Argonne scientists have pioneered the useof l_quid metals, particularly gallium, which is much more effective as a coolant. Atthe current stage of development, APS-designed optics can withstand the powerdens_ities associated with beams carrying brilliance levels in the 1018 range. Further

j optindzation of that geometry will be carried out to accommodate the even greaterpower densities that will c_me with the I019 brilliance level produced by the fullyoperational APS facility.

Acce..eJ'ator physicsAnti_:ipating the behavior of particles in a storage ring is among the most

daunting of accelerator-physics issues. The APS Accelerator Systems Division (ASD)is performing a series of experiments using the Aladdin storage ring at theSynchrotron Radiation Center _n Wisconsin. These experiments serve as a check oncomputer programs that must predict the behavior of particle dynamics in the APSstorage ring, as measured in respor_.se to perturbations. Under experimentalconditions, APS simulations have proven to be very accurate. The measurementsalso resulted in specific determinations about the operational parameters of themagnets in th: Aladdin ring. conditions which were not known at that level ofdetail at that time, making this undertaking useful for scientists at Aladdin as wellas at AI_...

Vacuum chambers

There will be 240 sections of vacuum charr.lber, each approximately 15 feet long,in the storage ring alone. Three actual, though non-production, storage ring

i_ vacuum-chamber segments, complete with all welds, hardware, and ports, havebeen constructed by the Accelerator System_ Division. Fabrication of these chambersrequires ir_tr_cate we.l.ding to allow connection, of all segments in the ring. An

' innovative weld,.'ng technique has resulted from the R&D effort carried out withFerranti Sciaky, Inc., of Chicago.

• Configuring vacuum chambers to match ring curvature has not been a trivial• matter. It was realized that if the chambers could not be bent, they would require

machining, a _uch more expensive alternative. A method for bending thechambers, the subject of an R&D initiative begun two years ago togetber with PacificPipp. of Oakland, California, ha oeen successfully demonstrated, putting to rest a keytechnical and budget issue.

MagnetsAs there will be a total of 1503 magnets of various types in the APS accelerator

complex, R&D in this area has also been a focal point for the Accelerator SystemsDivision. The first of 400 APS storage-ring quadrupole (SRQ) magnets has beenassembled from components fabricated to APS specifications. The SRQ, though astraightforward electromagnet, is very demanding in terms of magnetic-fieldquality: Storage-ring quadrupoles for the APS require field gradients accurate to 1part in 104, maintainable even after disassembly and reassembly for repair. Criticalparameters must also be achieved economically over the entire SRQ fabricationcycle, as they must for all APS magnets.

The prototype 0.8-m-long SRQ was transported to Fermi National AcceleratorLaboratory for magnetic measurements, which proved to be within the requiredmargin of error. Slight design modifications are now under way prior to assemblyand testing of a second SRQ. In order to expedite the measurement process, an APSmagnet-measurement facility is scheduled to be on line at Argonne in the summerof 1990.

FUNDING

The 7-GEV Advanced Photon Source Conceptual Design Report proposed aconstruction budget of $380 million (expressed in FY1989 dollars, as are all amountshere), with $77 million of that sum for contingency and a detailed estimate totaling$303 million for technical components including the injector, the storage ring,insertion devices, and beamlines. Since then, that estimate has held up as the APSprogressed from conceptual design to a completion level of 30 percent. Though costshave risen by $30 million, the contingency has dropped to $49 mill':'a as moreknowledge about the design has been gained, the motivation for setting a largecontingency at the outset. Escalation in the cost of conventional construction,currently estimated at $I47 million versus the CDR estimate of $115 million, hadbeen the cause of some concern. However, in the last few months, value-

engineering studies have identified approximately $16 million in cost containmentsfor conventional-facilities construction. Over all, the project co'-' estimate has risenby only one percent.

The schedule now on file with the Department of Energy, the Office ofManagement and Budget, and the Congress, calls for $40 million in FY1990 tounderwrite early construction activities, as well to purchase some technicalcomponents. In FY1991, APS is scheduled to receive $75 million, with fundingescalating through _Y1993 and then tailing off over the next t,._o years for a total of$456 million at completion in 1995.

Project management has developed an accelerated funding profile, calling formore initial dollars but no increase to the total of $456 million, which would allow

completion of the APS a year earlier. That possibility has been communicated, andthere has been some enthusiasm for it within the Department and Congress.

These next few months will be critical to the progress of the Advanced PhotonSource. If the case for an accelerated funding schedule is made, perhaps the AIX3 will

10

have some chance of competing with next-generation facilities being constructed inEurope and Japan.

LEITERS OF INTENT

APS user programs are approaching an important date. May 1, 1990, has been setas the deadline for submission of' experiment proposals in the form of Letters ofIntent from prospective users, both Independent Investigators and CollaborativeAccess Teams. Those Letters of Intent that are approved will move on to the formalproposal stage. Finally, there will be a third stage, where a memorandum ofunderstanding is signed cementing relationships between users and the Laboratory.

Ali those associated with the APS can view May 1 as that point in time when thevariety and scope of research interests will come into clearer focus, and the APS'strue potential will begin to take shape concurrent with its physical manifestation.

11

Workshop on Atomic Physics at the Advanced Photon Source

Argonne National Laboratory, 29-30 March 1990

OPPORTUNITITES FOR ATOMIC PHYSICS WITH HARD SYNCHROTRON RADIATION

Bernd Crasemann

Department of Physics, University of OregonEugene, Oregon 97403

Introduction: Construction of third-generation synchrotron-radiation facilities places atomic and molecular scientists at

threshold of extraordinary opportunitites.

Complementarity of APS and ALS. Here emphasize applications

of hard x rays.

History of x rays recent. Importance in development of

"modern" physics--crucial experiments on wave-particle dualism,structure of matter.., yet limited. Continuous source of EM

radiation from transverse acceleration of charged particles seen

in supernova remnant in Crab. Properties of SR from synchrotrons

and storage rings predicted IB98 by Li_nard, cf. also Schott 19i5,

calculated by Schwinger 1946, '49 and Sokolov and Ternov 1968.First observed in 1947, initially considered nuisance. Only in

last 3 decades the realization has grown that this source of

radiation---continuously tunable, highly polarized, bright---is

extremely useful for scientific research and technology.

Potential in atomic physics strikingly revealed by experiment of

Madden and Codling 1963. Yet lags behind e.g. surface science,

crystallography.., largely because of tenuity of gas-phasesources and relatively low cross sections. Change now: insertion

devices, dedicated third-generation sources---anticipate

extraordinary advances in applications.

These perspectives were surveyed by a Panel at a Do___E_Workshopheld in Berkeley last November; its report and those of other

panels dealing with additional frontier research areas in AM0sciences are to be discussed at a "town meeting" on the last

evening of the DAMOP annual meeting in Monterey 21-23 May. Ap-

propriate to take the Panel Report as starting point here, expand

upon unique potential of hard x rays in the production of whichthe APS will excel.

Subjective view of "Global Frontiers" (note qualifiers). Strongpotential of APS likely to lie in part in exploration of relati-

vistic and EO_effects which become prominent in inner shells and

at high Z---cf. later.

Techniques and topics---provide selected illustrations:

Total photon interaction cross sections [Absorption spectromet-ry] ....Technological applications from medical radiology to space

travel---discrepancies near edges; mar_y-body effects; ill-unders-

tood phenomena. Clear resolution at ix_ner thresholds---cf. Xe LS---need to extend.

12

Scatterinq---Molecules and atoms to nuclei; cf. George -9Brown's lecture---nuclear Bragg scattering, resonance width 10

eV! Fe-57 in YIG, sees enhancement o_f_fcoherent decay: broadening

and shift; qaantum optics analog.

Fluorescence---cf. Lindle et al.'s discovery of polarizationdependence of Cl K-beta from CH3CI (methylchlorlde) on excitationenergy in the C1K region---deduce molecular orbital symmetries

(Peter Langhoff): a consequence of the alignment of the molecule

produced by the excitation process. Foresee applicability to more

complicated molecules, adsorbate and condensed phases!

Photo- and Auger-electron spectrometries---workhorses of atomic-

structure and dynamics investigations, anticipate more angle- and

spin-resolved and coincidence measurements made possible by high-er brightness---cf. Manfred Krause's lecture.

Especially fruitful now: e-e correlation studies by thres-

hold ("zero-energy") tlme-o_-flight electron spectrometry.

Further example: Tulkki-Krause Xe 5s threshold satellite:

cross section at t_reshold dominated by Interaction between !5s]single hole and 5p 5d double-hole ionization channels---new 'in___x_-

ternal electron scatterln_ satellite" with peculiar dynamical

properties dominates at threshold!

Ion spectrometry---Note paucity of data. Frontier. Cf.

Wuilleumier lecture. Church reviewed andrecently brightness

storage techniques. Plans for tr___s incl. EBITs in SR beams.

For remainder of talk, turn in slightly more detali to a couple

of challenging questions regarding atomic inner-shell phenomena ....

A sDecial re i_in which APS will lend access to unprecedentedexploration... Illustrate.

Atoms held together by the Coulomb force, hence it is importantto look at the lowest-order relativistic corrections to the

Coulomb energy, viz., current-current interaction [exchange of a

single transverse photon] and retardation effects.

Breit operator accounts for small contribution to total energy---

but can get significant in special cases, e_g. hyperfine split-

tings and two-hole-state energies...

Energy matrix element between antlsymmetrized j-j-coupled 2-hol_states.

Test p_ediction_ by locking at hypersatqllites, Note K-alpha-one-h [is ]-[_s2p]-Pllforb!dden in LS coupling, emission depends onmixinq of _PI and P1 in [2s2p] final state---reduced by Breit:

25% effect at Z=lS---but mixing is increased for higher Z!

Note from classical ratio of two indiscrepancy K-alpha-one/K-

alpha-two hypersatellite intensity ratio vs. Z! What fun to check!

13

Similar large contributions of Breit to e_zr,e_Er_Ly_shifts---clearopportunity for sensitive tests of Mann-Jchnson operator.

Another class of atomic inner-shell processes that deserves being

singled out because important investigations w_Jl become possible

with the APS relates to virtual (i) Interaction of_henomena :hole states with the continuum, and (2) resonant Raman transi-

(' tJ ons.

Interaction,with-radiationless-continua effect on level energies.

Second type of interesting virtual transitions, barely explored

as yet: resonant Raman scatterinq.

Principle of Raman transitions.

Xe L3-M4M 5 threshold Auger spectra and hole-state width, compared_,ith ab_orptlon-edge "anatomy."

___ A later, better spectrum: consider potential in view of importancethat Raman spectrometry has gained in other fields.

Conclusion: chance to lead the [scientific] world!

2

T,

14

I

OPPORTUNITIES..... iii

FOR

WITH

BADIAT!_Q____.

15

(sp,z3+)

_9'_ _9_ 200 20'5 210WAVELF'NGTH [ ,_LNC,_T I_C_UlP-,I

16

Future Opportunities for Researoh inAtomio, Moleoular, and OptioaEScience

DoE WORKSHOP

II'_ERKKLEY, 7 NOVEHBER lg89

Puml m

RTOHIC RND MOLECULARSCIENCEWITHSYNCHROTRONRRDII:ITION

Tomas Baer, University of North CarolinaBernd Crasemann, University of OregonJ.L. Dehmer, Rrgonne National LaboratoryH.P. Kelly, University of VirginiaH.O. Kraose, Oak Ridge National Laborator9D.W. Lindle, Natl. Inst. of Standards & Tech

17

Gl_ib_ _rontiersin Scienceinolude

* STRUCTUREof atoms and moleoules andDYHRMICSof processes --

esO. near thrssholds

* MRNY-BODVEFFECT_Eleotron Correlations --

"Begond the Independent-Particle Hodel"

* RELATIVISTICRHOOED EFFECTSBREITSELF ENERGYVRCUUMPOLI:IRIZP,TION

4lee

rI

18

• Absorption spectroscopy- Absolute cross sections- Edge structure

• X-ray scattering- Absolute scattering probabilities- Depolarization of l-esonance fluorescene- Angular distributions

• X-ray fluorescence- Polarization/anqular distributions- Chemical, shifts- Multi-electron effects

• Visible-UV fluorescence- Molecular fragmentation- Molecular vibration/rotational resolution

• _ectron spectroscopy- Cross sections, angular and spin distributions- Multielectron effects- Resonant photoemission• i

- Post-collision interaction

• Auger-electron spectrometry- Auger ylelds- Energy levels of multiply charged ions- Satellites and many-elecWczon effects- Time-resolved studies- Threshold resonances- Cascade effects- Post-collision interaction- Angular distributions- Spln-resolved spectrometry- Coincidence studies

Q Ion spectroscopy" - Molecular fragmentation

- Multiple ionization- ' Ion coincidence studies- Studies of trapped ions

•- Two-color experiments

19

2O

ii

• ill

V()Z.UMI:63, NtJMJ31!_t15 PIIYSICAL REVIEW LETTERS 9 OCTOBER 1989

Resonance Energy Shifts duringNuclear Bragg Diffraction of X Rays

J. Arthur, G. S. Brown, D. E. Brown, and S. L. Ruby

Sta,_ford Synchrotron Radiation Laboratory, P.O. Box 4349, Bin 69, Stanford, California 94309(Received 12 June 1989)

We have observed dramatic changes in the time distribution of synchrotron x rays resonantly scatteredfrom STFe nuclei in a crystal of yttrium iron garnet, which depend on the deviation angle of the incidentradiation from the Bragg angle. These changes are caused by small shifts i_ithe effective energies of thehyperfine-split nuclear resonances, an effect of dynamical diffraction for the coherently excited nuclei inthe crystal. The very high brightness of the synchrotron x-ray source allows this effect to be observed ina 15-min measurement.

PACS numbers: 76,80.+y, 07.85.+n, 42.10.Qj, 61,10.Dp

500 --, _ ....... r • .... _""' '"_ "'" '" _ "'"' "'q

400 I1

._ _ , (b) 50=+31 }.trad '

E 3O0

'_ , '

==200

VO t . .'. 1 ,I.

0 50 100 150 200 250

Time (ns)

z

FIG. I. "lime distribution of resonantly scattered x ray:,-

from YIG (002) in symmetric Bragg geometry, with tl_e indi-cated deviation angles from the Bragg angle (corrected for re-fraction due to the electron density). Each solid curve gives

° the intensity of the Fourier transform of the dynamical theorycalculation for the multilevel energy-dependent reflectivity am-

plitude.

PHYS. REV. LETT.60, 1010 (1988)

Polarization of Molecular X-Ray Fluorescence

D. W. Lindle, P. L Cowan, R. E. LaVilla, T. Jach, and R. D. DeslattesNational Bureau of Standards, Gaithersburg, Maryland 20899

q

B. KarlinNational Synchrotron Light Source, Brookhaven National Laboratory, Lipton, New York 11973

and

J. A. Sheehy, T. J. Gil, and P. W. Langhofl"Department of Chemistry, Indiana University, Bloomington, Indiana 47405

(Received 7 December 1987) "i'.__,,,_2r:,¢

Polarization of CI K,B x-ray fluorescence following selective excitation of gaseous CH._CI with syn-chrotron radiation is reported. The degree of polariza!ion .of the fluorescence depends sensitively on thechosen incident excitation energy in the CI K-edge region. Theoretical considerations indicate that the

fluorescence-polarization measurements can provide directly absorption and emission anisotropies,molecular-orbital symmetries, and relative fluorescence transition strengths.

PACS numbers: 33.20.Rm, 33.50.Dq, 33.90.+h

:tO.00 _ , ,.o

,-. %>,, ,.,..

4-J

4.J B •12:"_ 5. O0 "' :

f

li.:. "> . . ; •

.t--_

4J

r-'-I .: a , ...L ' .z

...,:...,. •_'.._,/0.00 ........ - ....... , -, - '-'_

2.80 2.el 2 82 2.83

Photon energy (keV)

FIG. 2. CI K3 fluorescence spectra from CH3CI followingCI Is--* 8at excitation with 2823.4-eV photon energy, centeredon feature D in the absorption spectrum of Fig. I. The labelsparallel and perpendicular refer to orthogonal orientations ofthe measured fluorescence polarization relative to the incidentE vector. The two spectra have been scaled so that the areas of

peak C are identical. The peak at 2823.4 eV is due to elasticscattering of the incident radiation.

22

PHYS.REV. LETT.62, 2817 (1989)

Muitiple Excitation at Xezon 5s Photoionization Threshold

2 "l'ulkki

Research Institute for Theoretical Physics, Unit'ersity of He!sinki, 00170 Helsinki, Finlandand Laboratory of Physics, flelsinki Umrersity of Technology, (,) 02150 Espoo, Finland

(Received ,28March 1989)

The effect of multiple-electron excitation on the threshold behavior of Xe 5s photoionization is studied

using the multichannel multiconfisuration Dirac-Fock method with full account of relaxation. The in-clusion of the ionization channels related to 5p"5d .]ion " 7 excited states is found to change the single-

excitation results drastically. Our cross section and asymmetry parameter/3 are in very good agreementwith experiment. Calculation of the related satellite cross sections predicts a new type of satellite thatexists only in the near-threshold region and has a peculiar ang,ular dependence.

PAtsn,o,bo,: 32.SO.Fb [5s] "_%

5p45d _- (a)

, ..,_ 2015 ______..._.._=_7 -- _ 1.0 v

0.5 _- '_ "'" .....t.. ; V ,,.,., - "

0.0 L. v ..-"" r.:.. _ 0.5 Vv . -"

. ,,,'

-1.O _ ""' , ', ' _ , I , _ • '

(b):E

o • 1.3._ "... - _,0 0.I0 11 .._

co 0.90.05 . --

-. 0 0.7 rn

0.00 ........... 0.5 I,,")

30.0 35.0 400 45.0 50.0 55.0

Photon energy (eV)

5p45d photoelectron satellites

_ Experiment: Fahlman Krause Carlson and Svensson_ I ! I !

° Phys. Rev.A 3...Q,812 (1984)_

- 23

..... i ii

i, I I I I I i i ..... III ii I IIii 1 • --.-.jI

From Church et al., Physical ReviewA 36, 2487 (1987).

Signals from argon ion charge states, obtained using axial detection of the ions ina Penning ion trap. The ions were generated by a vacancy cascade followingsynchrotron radiation photoionization of argon.

24

'_11' II

ATOMIC INNER SHELLS_

LARGE ENERGIES e.g. E(ls) _----100 keV, Z _--87

---->ISTRONG REL.+ GED EFFECTS l*

m/mo =_1o05at Z/n = 43, also Ar -->AIE(ls)I ---5% at Z ---61

STRONG_TRANSITIONS e.g. r'(M1) _-_-20 eV, Z --90

MOSTLY RADIATIONLESS. e.g. o)(M1).-=-10-3, Z =70

MANY..CHA.NNEL_ e.g. 2784 matrixelements to [2P3/2]at high Z

VERY,,£HORT"_'s (< _'BOHR)

---> PERTURBATION APPROACH PUSHED TO LIMIT

TWO-STEP SEPARATION OFEXCITATION/DEEXCITATIONBREAKS DOWN *VIRTUAL PROCESSESPLAYIMPORTANT ROLE

* ILLUSTRATE -

25

m

_f__lT' Ir,IT-IF-I_ACT'IO r,_-

J'='lf_ST _OYNP, m_C-- C_I_I_.CTI_P4 "TO THE.

E LEC Tf_.OST'_TI¢ C_uI...0 lMr_ I I_'i-_-i_A CTIO N

[ I_ TH_ {'_.(=.-I,.. AT'i q_ $ T, C.. H At'_ tL.TON, I Ab"

G. Breit, Phys. Rev. 39,616 (1932)

- , ( L __-_OA_]_. L _ P,C_TH

e2 [_, •aj + (ai" riJ)("J" ru)JH_,,,,=-Z _ ' "r'i_ ]

=_ + 1 _ (a, r,_)(aj,ro)]ru "2 ru - _ rua J

- I I[ - _r -- [

magnetic retardation

J.B.Mann&W.a.Johnson,Phys.aev.A4,41(1971) (F'RE(_U_N¢_',_P(_(1

HBreit(w) = - -- [a, • aj cos oorii + (1 -- COSwri))]

retarded Gaunt retardationcorrection to

1_4 C01_P_ It._TE, I_ the charge-charge

_R.EIT- ¢-.._l,._{3 HII_¢IILT_ NIAI_: interaction

_¢_r _.

26

Breit-Coulomb energy matrix between j-jcoupled antisymmetrized 2-hole states:

(jlj2JMl r_t(1-ff l'_'2)cosa_r12 [jtj2JM ) =D-E

® [Jt J2 J Jl Jl k J2 J2 k

D=_, (--l)l+J(2jt+l)(2j2+l)lJ2 Jt L _ _ 0 Ja.=o -T -2" -T T 0

I ( Vtty_+tV,, )_'_ ( Vt t Y_- l V,, ) + 2LL++13 ""× ( Wt lY_ _22 ) + 2k-- 1 ""

4xltq

X II(IlMr)-(1 -_',xo) k(k+ 1) ( Utly_.U22 ) irl (li k+l ll)

and2

® [Ji Jz d Jt J2 L

E = _ (2jl + 1)(2j2 -t-1) _tjl j2 3. i t_.=o --T T 0

(p_2yx_tpXzt)+ (QXl2y_.+tQ_,) II(ltkl2)

(Kl+K2)2

--(1--rX°) L(L+I) (UI2YkU21)H(II k+l 12) ,

where

<x,v,_,_x,j>=lo"fo" x,,j,(,,)y_t(rlr2)

XXii(rz )dr ldr2 ,

w,j(_)=_j,,_)_j(_)+F,(,)Fj(_),

/';_(r)= _--t(_:---_)Uu(r)+ Ej(r),

Q,_(r)=(_+l)-_(xj x,)U,j(r)-V,:(r),, Chert et al.Phys. Rev.A 2___5

Uij(r)=G_(r)Fj(r)+Yi(r)Gj(r), 391 (1982)V,j( r) ----Gi( r )Fj(r ) --Fi( r)Gj( r) ,

and

{; ifl,+L+l:ziseven1-I (t __LI2)= otherwise

28

X-__' HYrEF_SAT'_._m_ITF..5s IMI -- II __ IIII III

_r I "L_--_ i iii i iiii i IIII1_

20 30405060708090Z

.FIG. 8. The.Ka_-to-Ka[x-rayh2_ersatelliteintensityrauo, as a function of atoms¢ number Z.

FromPhys.Rev.A2_5,391 (1982).

30

From Phys. Rev.A 25, 391 (1982).

3O 4O 5O 6O 7O 8O 9OZ

FIG. 4. Contribution (in percent) of the Breit energy

to the energy shif_ of .Kal and K/Yl hypersatellites with,_'°*'erenceto the respective diagram lines.

: 'Tlrl.e _'_, f rSrCSAq ?_.._ _T'_ ?_.__P-..C='_

31

_VIRTUALPHENOMENAIN ATOMIC INNERSHELLS:

(a) _Hole-_,_;ateinteraction with radiationless continua

(b) Resonant Raman scattering

INTERACTION WITH CONTINUUM-

Dynamic relaxation process" core hole fluctuates tointermediate CK level+ creates electron-hole pair excitation

[M. Ohno & G. Wendin,J. Phys. B 12, 1305 (1979)]

--> Many-body radiationless analog of the electron self energy!

I Narrowing of F'sCausesL Level Shifts 4,

IU. Fano, Phys. Rev. 124, 1866 (1961)]

32

EVEN FOR INNER SHELLS,

,DYNAMICS OF ATOMIC PROCESSES AREINTIMATELY LINKED TQ THEIRMANY-BODY CHARACTER-

PARTICULARLYNEAR THRESHOLD

EXAMPLE'PHOTOIONIZATION FOLLOWED BY AUGER DECAY

IN HIGH-ENERGY LIMIT,,INDEPENDENT-PARTICLETWO-STEP MODELAPPLIES RATHERWELL:

BUT NEAR THRESHOLD,A SINGLE SECOND-ORDER QUANTUMPROCESS TAKES PLACE

("RESONANT RAMAN")

34

i

e

dh RESONANT",r RAMAN

TRANSITION

*,INTERMEDIATESTATE IS VIRTUAl_" NO RELAXATION

* EMITTED LINE SHAPE = INCIDENT LINE SHAPE"CAN BE << ['!

* EMITTED ENERGY DISPERSED WITH INCIDENT ENERGY

.... > NOTE POTENTIAL OF EXPLORATIONWITH THIRD-GENERATION SYNCHROTRON-RADIATIONSOURCES!!

35

NEW FRONTIERS IN X-RAY PHOTOIONIZATION

OF IONS AND ATOMS

Steven T. Manson

Department of Physics and Astronomy

Georgia State UniversityAtlanta, GA 30303

ABSTRACT

Opportunities opened up in the area of photoionization of ions

and atoms by a high-brightness tunable x-ray source are discussed.

38

I. INTRODUCTION

A high-brightness tunable x-ray source, such as a synchrotron,

would be an extremely useful device for atomic physics studies.

Since the coupling between the x-ray photons and the target is weak

(of the order of the fine-structure constant, ~ 1/137, compared to

coulomb coupling), the dynamics of the target can be investigated.

A high-brightness photon source is needed to produce enough counts

to do an experiment in a "finite" time (where "finite" is related

to the lifetime of the beam) where the target density is low.

Target density may be low because it is difficult to create such

a target, such as in the case of multi-charged positive ions. In

addition, target density may be kept low intentionally, so that

emerging electrons are not scattered on their way out of the

interaction region before they are detected. Thus, a high-

brightness x-ray synchrotron opens (or enhances) the possibility

of a number of experimments concerning ions and atoms. In this

paper, some of the emerging possibilities are outlined; it is meant

to be indicative, not exhaustive.

II. Photoionization of Ions

The extant experimental data concerning photoionization of

ions is quite sparse, and practically all on singly-charged ions,

and less than ten of those. 1"3 Some examples are experimental cross

sections for singly charged ions are shown 4"6 in figs. 1-3. Where

comparison with theory has been made, as in the case of K .,

agreement is quite good z as seen in fig. 4. There is also some

experimental data on Ba .2 multi-charged ions of carbonS; an example

39-

is shown in fig. 5. It is to be emphasized that this is the

totality of published experimental data!

The conventional wisdom has been that electron dynamics get

simpler in going to more and more highly charged ions. While this

is true eventuallM (and the word eventually is to be stressed), it

does no happen quickly or montonically. The experimental data

shown in fig. 5 does not appear to be getting simpler with

increasing stage of ionization, for example. In addition, a

theoretical study of the excited nf states of the Cs isoelectronic

sequence 9 provides a dramatic counter-example to the conventional

wisdom. The nf cross sections for Cs, fig. 6, are monotone

decreasing and simple, while Ba ., fig. 7, they are considerably

more complex. As a matter of fact, looking at the 6f cross

section, fig. 8, it does indeed take some time before the cross

section is simple again; even Tb .10 is not enough!

In _ddition, theory predicts a simplification for inner shell

photoionization of ions1°; namely, except for a shift in the

threshold energy, inner shell cross sections do not change with the

removal of outer shell electrons. Examples for Fe 2s and 3p are

shown 11 in figs. 9 and i0. It is to be emphasized t_t there is,

as yet, no experimental confirmation of this simplification.

Clearly benchmark measurements over a broad range of Z (nuclear

charge) and N (number of electrons) are needed. Since most of the

cross sections are in the X-ray range, and target densitites are

apt to be low, a high-brightness x-ray synchrotron is ideal for

this purpose.

Furthermore, the study of auto-ionizing or auger resonances

- 40-

in the photoionization cross section, which are so important for

neutral atoms and low-charges ions, should be quite instructive

since the importance of these resonances should decrease since the

branching ratios (fluorescence yields) favor radiation over

electron emission for highly charged ions. The situation is shown

schematically in fig. ii.

Finally, note that it has been shown 12 that the x-ray and auger

channels for the decay of an inner shell hole cannot be treated

independently but interfere with each other; inner shell

photoionization of ions are ideal "laboratory" for this effect, not

yet studied experimentally.

III. PHOTOIONIZATION OF ATOMS

Atoms are relatively easier to get reasonable target

densities, but the densities must be limited to do electron

spectroscopy. An extremely interesting but poorly understood

region is in the vicinity of inner-shell thresholds. While therez

is a significant amount of atomic photoabsorption data in the x-

ray range 13, there is almost nothing within 5 or i0 eV of threshold;

some examples are shown in figs. 12 and 13. Studies of inner-shell

photoionization in the threshold region of open-shell atoms reveal

details of correlation and particularly exchange. Calculations

predict strong effects 14, even for systems as simple B 2s shown in

fig. 14. Such investigations are important to the study of open-

shell atoms which, after all, make up most of the periodic table!

In addition, inner shell photoionization of all atoms is of

importance since these studies can shed light on the three-.body

4!

continuum coulomb problem, one of the oldest unsolved problems in

physics. Ideally, studies of energy and angular correlation of the

photoelectron and an auger electron are needed. This, of course,

requires a bright x-ray source. This process is shown

schematically in fig. ]5.

Studies of photoelectron angular distributions in the x-ray

region is also of great interest since this process gives

information of high order multipoles, not just dipole.

Furthermore, although higher multipoles contribute to the total

cross sections as well, they are much more important in angular

distributions owing to the interference terms in the angular

distribution which are not there in the total cross section.

Further, the importance of higher multipoles is clearly revealed

in a non-dipole "signature" of the angular distribution.

ACKNOWLEDGEMENTS

This work was supported by the U. S. Army Research Office and

The National Science Foundation.

42

REFERENCES

i. K. Dolder in Electronic and Atomic Collisions, eds. H. B.

Gilbody, W. R. Newell, F. H. Read and A. C. H. Smith (North-

Holland, Amsterdam, 1988), pp. 549-556.

2. F. Combet Farnoux, J. Phys. (Paris) 49, C7-3 (1988).

3. S. T. Manson in Electronic and Atomic Collisions (to be

published, 1990).

4. T.B. Lucatorto and T. J. McIlrath, Phys. Rev. Lett. 3_, 428

(1976) .

5. T.B. Lucatorto, To J. McIlrath, J. Sugar and S. M. Younger,

Phys. Rev. Lett. 4_/7, 1124 (1981).

6. I.C. Lyon, B° Peart, J. B. West and K. Dolder, J. Phys. B 1__9,

4137 (1986).

7. G. Nasreen, P. C. Deshmukh and S. T. Manson, J. Phys. B 21,

L2_ (1988).

8. E. Jannitti, P. Nicolosi and G. Tondello, Phys. Scr. 41, 458(1990).

9. L. Lahiri and S. T. Manson, Phys. Rev. A 37, 1047 (1988).:

i0. R. F. Reilman and S. T. Manson, Ap. J. Supp 40, 815 (1979).

Ii. R. F. Reilman and So T. Manson, Phys. Rev. A 18, 2124 (1978).

12. L. Armstrong, Jr., C. E. Theodosiou and M. J. Wall, Phys. Rev.

A 18, 2538 (1978) .

13. E. B. Saloman, J. H. Hubbell and J. H. Scofield, At Data Nuc.

Data Tab. 3-8, 1 (198'7).

14. S. T. Manson and S. K. Bhattacharya, Aust. J. Phys. 39, 799

(1986) .

_- 43i

=

From Phys. Rev. Lett. 37, 428 (1976)

| I I II I I I I _ III I II IIH

i (6, ,,_ l__ _ ,nstrums_ltaS Re$o,ut,on

I I

_: "---.-......_... , • .. , 2pS2P3/__3dT4sZ

< 1.3d _ I=:: ,_ 2P12pS /2

__1

i j L,, i L, i I .... ,, I___ I ' •

32 30 28 26

WAVELENGTH(nm)

i. Experimental photoabsorption cross section for (a) Na and (blNa T from Ref. 4.

44

40 _._S. 4a92D5/2_Ba ++

,oo 16o

'2. ExpeHnienl,al phot, oab:;orpti(,n cross s_:ction for Ba, Ba + and Ba +2

From Phys. Rev. Lett. 47, 1124 (1981 )

45

Photon energy (eV)21.2 I 21.3 21.4 21.5 21.6I

-------- _ i I i I I4-

I1.

T

25- _,,• ,

'1

20-T

I ...O '

'- 1

E

_ 15©

° tffl

_ I

_it t t ,: . _

\ t

1 \

0

3. Experimental photoionization cross section for Ba. (Lyoneta].)

Adapted from J. Phys. B 19, 4137 (1986)

46

(_wo _L-OI.)NOI].D3S SSOU©

4. Photoionization cross section of K+ from Ref. 7. The points

are experimental, the upper curves are calculated relativisticramdom phase approximation results with and without intershell

coupling, and the lower curve is the calculated central-field• result.

47

From Physica Scripta 41,458 (1990)

i0l ' ls2 1S" lsnp 1po1 . 71_514 3 £1I

CV ,o.5 II4I

K

o,8_ CJvii

0,4L I

I

,Kti

1._L

CIII

IAI,! '0,01 'lJ t _i,u _.,

25,0 30,0 35.0 40.0 ,45,0 ,/,

5. Experimental absorption coefficient of ions of carbon in the

region of the Is threshold from Ref. 8. The dashed line in

the C V spectrum is te theoretical result of Ref. i0.

48

From Physical Review A .,_.Z,1047 (1988)

4f

5f,"!/

/J

, Calculated photoionization cross sections for excited nfstates in Cs from Ref. 9.

From Physical Review A ._3.Z,1047 (1988) ., 5f

//

//

/

" Ba/// 1 +'8f

I// I i101 19f

tl '

1°° Ii sf

,,_ 10"1 !L L __ , , , ,

I ! /1 6f /,"v 10-2 _ i ' ' '

b s"i / I "/

't 7f /

10-3 - ' - ._v'II

10-4:_ I, .....i

,.

10_5{, 9fi j ,,

0 1 2 3 4 5

6, R

7. Calculated photionization cross sections for excited nf statesin Ba+ from Ref. 9.

5O

FromPhysicalReviewA .,3!,1047(1988)

101 I I 1 I I

loo 6f

. 10-3

o 1

10-4 , l t0 1 2 3 4 5

G / R8. Calculated photoionization cross sections for excited 6f

states in the Cs isoelectronic series from Ref. 9._

= 51

From Physical Review A 18, 2124 (1978)

9. Calculated 2s photoionization cross sections (per election)for ions in the Fe isonuclear series from Ref. ii. Thevertical lines are the thresholds for the given stage ofionization.

52

From Physical Review A 18, 2124 (1978)

0.05

5 10 15 20 25

hIJ(RYDBERGS)

i0. Calculated 3p photoionization cross sections (per election)for ions in the Fe isonuclear series from Ref. ii. The

vertical lines are the thresholds for the given stage of

ionization.

53

Adapted from Aust. J. Phys..3.._,799 (1986)

1.0I 1 L -0 1 2 3 4 5 6

hU(RYDBERGS)

14. Calculated branching ratio of 3p:ip final states in 2s

photoionization of B from Ref. 14. The curves labelled L and

V represent "length" and "velocity" results, while K includes

only the shift of thresholds. Note that in the absence of

dynamical effects, this ratio should be three.

57

DETECTORS

ee

/////,,," ////II

I III I I

+hv

A A A _ A A _,* _

15. Schematic representation of photoelectron-auger electron

energy and argular correlation (coincidence) experiment.

58

Advanced

: Light

Source

THE ADVANCED LIGHT SOURCE:A NEW 1.5 GEV SYNCHROTRON

RADIATION FACILITY AT THELAWRENCE BERKELEY

LABORATORY

Fred Schlachter

University of CaliforniaLawrence BerkeleyLaboratoryBerkeley, CaliforniaUSA

59

r_._A_dvance d

THE ADVANCED LIGHT SOURCE

The Advanced Light Source (ALS), presently under construction at theLawrence Berkeley Laboratory, will be the world's brightest synchrotron-radiation source of ultraviolet and soft x-ray photons when it opens its doors tousers in April 1993. The ALS is a third-generation source that is based on alow-emittance electren storage ring, optimized for operation at 1.5 GeV, withlong straight sections tbr insertion devices. Its naturally short pulses are idealfbr time-resolved measurements. Undulators will produce high-brightnessbeams from below 10 eV to above 2 keV; wigglers will produce high fluxes ofharder x-rays to energies above 10 keV.

The ALS will support an extensive research program in a broad spectrumof scientific and technological areas. The high brightness will open new areasof research in the material.s sciences, such as spatially resolved spectroscopy(spectromicroscopy). Biological applications will include x-ray microscopywith element-specific sensitivity in the water window of the spectrum wherewater is much more transparent than protein. The ALS will be an excellentresearch tool for a_omic physics and chemistry because the high flux willallow measurements to be made with tenuous gas-phase targets. Undulatorradiation can excite the K shell of elements up to silicon and the L shell of'elements up to krypton, and wiggler radiation can excite the L shell of nearlyevery element.

The ALS will operate as a national user facility; interested scientists areencouraged to contact the ALS Scientific Program Coordinator to exploretheir scientific and technological research interests.

Fred SchlachterScientific Program CoordinatorAdvanced Light SourceMS 46-161Lawrence Berkeley LaboratoryBerkeley, CA 94720

60

THE ADVANCEDLIGHT SOURCE:SOME ESSENTIALS

Designed for the VUV and softx-ray region; optimized for 1.5-GEVelectron beam energy

-_ Based on an electron storage ringwith 12 straight sections, 197 meters incircumference

_ Includes provisions for about 60beamlines, including 11from insertiondevices

.Stored beam to have extraordinarilylow emittance,short pulses

Construction now under way at theLawrence Berkeley Laboratory; to beoperational in April 1993

61

The ALS and APS complement eachother

Wavelength ot_) o°104 103 102 1 1,,

_: _I ' ' I "' .....' 'I ' ' I ' ' I ' ' .£13

1020-_9, - ALS Undulators,--- APS -

0 - U3.9 Undulators

. -[;:::1018" _

E - u8_,/-- _

e4 "" ' N "

. _ _ 'E_ 016 -k_. I -- "-

E - w13.6-

0O

_1014 -C0 -

0c-

13--1N 12- , i I , , , I , ,, _ ,/ _.J¢

10° 101 102 103 104 105

Photon Energy (eV)

62

A Brief History ofSynchrotron Radiation

The instantaneous total power radiated by a nonrelativistic electron was first expressed by Larmor

in 1897, using .classical electrodynamics:

p_ 2 e 2 I_.,lluvl23 e3 Idt, I

-h-Synchrotron radiation was first observed at the GEResearch Laboratory in Schenectady, NY in April1947, on a 70 MeV electron synchrotron built partlyto test McMillan's synchrotron principle.

_r A 7-pole wiggler was used as a synchrotronradiation source at SPEAR in 1979.

_r Halbach's idea of using strong permanent magnetsmade from rare-earth elements and cobalt instead

of electromagnets made undulators practical VUVand x-ray sources.

_A permanent magnet undulator developed jointly byLBL and SSRL was installed at SPEAR in 1980. Its

output was four orders of magnitude higher thanthat from a SPEAR bend magnet.

63

MODERN SR RESEARCHFACILITIES

"First Generation" facilities were initially parasiticoperations at existing high-energy physics facilities:

ADONE Frascati, ItalySSRL/SPEARat SLAC Stanford,CADORISat DESY Hamburg,W. GermanyCHESS/CESRat Cornell Ithaca,NYVEPP2M andVEPP3 Novosibirsk,USSR

"Second Generation" facilities are dedicated buthave limited magnetic insertion device capability:NSLSat BNL LongIsland,NYAladdinatWisconsin Madison,WlB_Y WestBerlinPhotonFactory Tskuba,JapanSuperACO Orsay,France

"Third Generation" storage rings are specificallyoptimized (long straight sections and low beamemittance) for magnetic insertion devices:ALS at LBL Berkeley, CaliforniaTSL (SRRC) Hsinchu,TaiwanSiberiaII (Kurchatov) Moscow,USSRBESSYII West BerlinSincotroneTrieste Trieste, ItalyPLS Pohang,Korea

Al:X3 Argonne,illinoisESRF Grenoble,FranceKansai6 GeVring Osaka,Japan

64

Synchrotron-radiation facilities areproliferating

L.Q.C.ATION R]._a_L[.,2L_ ELECTRON ENERGY NOTES(GEV)

BRAZILCampinas LNLS 2.0 Dedicated*

CHINA (PRC)Beijing BEPC (IHEP) 2.2-2.8 Partly DedicatedHefei HESYRL (USTC) 0.8 Dedicated*

CHINA (ROC-TAIWAN)Hsinchu SRRC 1.3 Dedicated*

ENGLANDDaresbury SRS (DARESBURY) 2.0 Dedicated

FRANCEOrsay ACO (LURE) 0.54 Dedicated

DCI (LURE) !.8 DedicatedSuperACO (LURE) 0.8 Dedicated

Grenoble ESRF 6.0 Dedicated*GERMANY

Bonn ELSA 3.5 Partly DedicatedDortmund DELTA 1.5 Design/FEL useHamburg DORIS II (HASYLAB) 3.5-5.5 Part!y DedicatedWest Berlin BESSY 0.8 Dedicated

BESSY II 1.5-2.0 DesignfDedicated

INDIAIndore INDUS-I (CAT) 0.45 Design/Dedicated*

INDUS-II (CAT) 1.4 Design/Dedicated*KOREA

Pohang Pohaag Light Source 2.0 Design/Dedicated*ITALY

Frascati ADONE (LNF) 1.5 Partly DedicatedTrieste Sincrotrone Trieste 1.5-2.0 Dedicated*

JAPANOkasaki UVSOR (IMS) 0.6 DedicatedKansai area 8 GeV Ring 6.0 Design/DedicatedTokyo SOR (ISSP) 0.4 DedicatedTsukuba TER? S (ETL) 0.6 DedicatedTsukuba Photon Factory (KEK) 2.5 Dedicated

Accumulator Ring (KEK) 6.0-8.0 Partly DedicatedTristan Main Ring (KEK) 25-30 Planned Use

SWEDENLund Max (LTH) 0.55 Dedicated

USAArgonne, IL APS (ANL) 7.0 Design/DedicatedBerkeley, CA ALS (LBL) 1.5 Dedicated*Gaithersberg, MD SURF II (NBS) 0.28 DedicatedIthaca, NY CESR (CHESS) 5.5-8.0 Partly DedicatedStanford, CA SPEAR (SSRL) 3.0-3.5 Partly Dedicated

PEP (SSRL_ 5.0-15.0 Partly DedicatedStoughton, WI Aladdin (SRC) 0.8- ! ,0 DedicatedUpton, NY NSLS I (BNL) 0.75 Dedicated

_- NSLS II (BNL) 2.5 Dedicated

Baton Rouge, LA LSU 1.0 Design/Dedicated*USSR

Karkhov N-100 (KPI) 0.10 DedicatedMoscow Siberia ! (Kurchatov) 0.45 Dedicated

Siberia II (Kurchatov) 2.5 Dedicated*Novosibirsk VEPP-2M (INP) 0.7 Partly Dedicated

VEPP-3 (!NP) 2.2 Partly DedicatedVEPP-4 (INP) 5.0-7.0 Partly Dedicated

* In construction or approved for construction as of 12/88

65

AN EXPLOSIVE GROWTH INBRIGHTNESS IS DRIVING THE

PROLIFERATION OF THIRD-GENERATION SYNCHROTRON

SOURCES

" 66

Brightness• intensity° narrowness of spectral distribution• ease of focussing

Brightness: an importantmeasure of quality

67

..........Z,<

_<

_ 101 ..............

_m

Ut.,.uJ _

_ 101zIi. r i i ii i,iiiii

ELI ,==IL3_

_1 w,J

/ ROTA'nNC'ANODE1o9 ..........ELEC'I'RON-IMPA_-r'X-RAY ' _*X-RAY TUBES

_ /TUBES INTRODUCED _ INTRODUCF_D

106 ,,1900 1920 1940 1960 1980 2000

]}RIGHTNESS OF X RAYS has izlcreased l=ryma_ orders of mag_tude since the adv_tof s3_cb.rotro_d._Ucm sources. Undulators in storage rings are the briE31te_ source.

68I

Technological advances have madepossible third-generation synchrotron-radiation sources

• Accelerator physics..........low-emittance lattices

° Accelerator construction.........CAD/CAM

• Insertion devices...........permanent-magnetdesign

• x-ray optics...........nanofabrication

7O

i

ALS CONSTRUCTION AT THELAWRENCE BERKELEY

LABORATORY

The following phot_)S show:

1 ) ALS construction site with model of finishedfacility, which will be ready for users in the springof 1993.

2) LBL site is on the hillside above the University ofCalifornia at Berkeley campus. Dome atop the old184-Inch Cyclotron building will crown the newALS building, as weil.

3) The ALS site stands out in this aerial view of LBL.

4) The 184-Inch Cyclotron, built by E.O. Lawrenceduring WWII, was the first major facility on thecurrent LBL site.

5) The ALS building will consist of an annularaddition surrounding the renovated cyclotronbuilding. Here the contractor is putting in thefoundation for the addition.

6) Structural steel for the addition was in place bythe end of 1989.

7) Diagram shows the main components of the ALSfacility.

71

Pl

77

VI'Y"_AJdvanced

_rLightI$ource

j'"" _ " TheAdvanc_ LightSource

/ ' and bend ng magnet "/E xPe',me n'al areas,L_'_'k_C-i' _.Z"_"_== ...... _a' beamne s

"--.- _L'_ ., I. ----__-___.-...,__X_"_-___-__-_----___-_ __..__---_.____ -,,_.

synchrotron radiation

'

i Monochromator |

Ex,_,,,__'- "'"_i""%.Y

78

CHARACTERISTICS OF THE STORAGE RING

ALS

• Store 1012 relativistic electrons for six hours

while controlling their positions to --50 microns

(in six hours they travel four billion miles)

• This _'equires

- Precisely'engineered magnetic lenses, dipoles, and higher

order correction magnets

- A sophisticated understanding of the dynamics of high

charge density electron bunches in non-linear magneticfields

- Precise beam sensors and feedback systems

- A vacuum channel for the beam of 10 -9 Torr, even with the

x-rays present to desorb gas from walls. Otherwise,

scattering on gas disrupts beam.

- A powerful radiofrequency accelerating system (--,300kW of

. power @ 500 MHz) to resupply the energy emitted as x-rays

- A very sophisticated control system to monitor and controlall of this

[

1 79z

" Ipl.... ,"rll IiU'""' mimlrII _'" " r, r _m_l, ' 'III...... _I,l_'_lm_'_"_i,ill'iU_,rl_'rql'l'_,IE!i,l

ALS electron beams are small

• typical dimensions: 120_m x 660_m

-this is 0.005 x 0.025 inches

- diameter of human hair: 80_m

• beam size and position must be carefullycontrolled

8O

--

ALS electron bunch structure

Gaussian pulse

• .-_,_\ (rms)

20% of C = 196.8 m - - \I FWHM>--35 pS

buckets I= 400 mA k"_ / iunfilled (1.6 mA per bunch)for _ion 328 buckets available, ]'FWHM = 2.35 _ timeclearing nominally operate

with 250 filled

|'FWHM "_ 35 ps (nominal)500 MHz RF

"V""V" l --II...... 2 ns ...... I

O O,,4 ..

35 ps 35 ps

" Schematic illustration of the electron bunch structure in the ALS

. storage ring during multibunch operation. As shown at the upper right, eachbunch has a full width at half maximum of about 35 ps. The spacing between.

bunches, dictated by the rf frequency, is 2 ns. (The electron pulse length is thus1.75% of the bunch-to-bunch interval. If rendered to scale, the illustration at

the left would show 250 narrow spikes, distributed around 80% of the ring's cir-

cumference.)

m=g

i

81

..

BEAM UNE II

C RAD_O-FREQUF._CAvn'Y

UNOULATOR :,

\

A

COIL WINDINGS

STORAGE RING dedicated to the production oi' synchrotron radiation is structuredaround a ring-shaped vacuum chamber through which a beam of electrons circulates.An oscillating electromagnetic field established in a radio-frequency cavity providesenergy to maintain the particles at relativistic speeds (nearly as fast as light) after theyare injected into the ring from an external accelerator (not shown). Quadrupole andsextupole Ibcusing magnets confine the electrons in a tight beam by means of fields setup by fbur and six poles, respectively, arranged radially around the vacuum chamber.Bending magnets three the electron beam to curve, causing the particles to emitsynchrotron radiation (black areas). The ring may also include other magnetic devicesknown as wigglers and undulators that substantially increase the "brightness" of theradiation_a measure of' its concentration. Pipes called beamlines channel theradiation ii'ore the various magnetic device.,_ to experimental stations.

- 82

_

ALS lay.out: i_j_to_,booste_,storage ring............1.5 GeV

\\

",, \

/ ",, _

/ _"%

! i \. 'i/ I_ /

\ '

,, 1.5 - GeV Booster " i

"_ Synchrot- "'.-,,,,Storage ring

012 4 6 8 10

Scale in meters

Main Parameters of ALS Storage RingBeam energy [GEV]

Nomina_ < 1.5;//

Minitt_).'_., ,, 1,0 .

Max,_'_,_m/ 1.9,, (

Circumference fm] 196.8

Beam current [mA] :.,

Multibunch ' 400Single bunch 7.6

Beam emittance, rms [nra.rad]

Horizontal 10Vertical 1

Relative rms momentum spread

Multibunch 8.0 X 10-4Single bunch 13.0 X 10-4

Nominal bunch duration, FWHM [ps] 30-50

Radiation lossper rum [keV] 92

Length available for insertion devices fm] 5

ALS triple-bend achromat lattice

/" B SD QFA SF B,! SF QFA SD B QD QF " "'QF QD ',

0 1 2 3lC ! r ,

Scale(meters)

One superperiod of the ALS triple-bend achromat lattice contains

three combined-function (bending and focusing) magnets (B), six quadrupole

focusing magnets (QF and QD), and four sextupole magnets (SF and SD).

= 84

ALS design: 3-d CAD*I

example:storage-ring sextupole magnet

* CAD: computer-aided design

_5

CAD DESIGNED ALS HARDWARE

The following photos show:

1 ) CAD drawing of ALS storage-ring sextupolemagnet and vacuum chamber.

2) Engineering model of sextupole magnet.

3) One-half of storage-ring sector vacuum chamber.Each half of chamber is machined from analuminum billet, then the top and bottom arewelded. There are 12 sectors irl the storage ring.

4) First article (prototype) of completed sectorvacuum chamber. Recessed cut-outs make roomfor storage-ring magnets. Titanium sublimationand sputter ion pumps are mounted below thechamber. Devices on top are actuators for photonstops that prevent synchrotron radiation fromreaching the walls of the chamber.

85

SYNCHROTRON RADIATIONSOURCES

The following illustrations show:

1 ) Sequence of diagrams shows the three main typesof synchrotron sources (bend magnets, wigglers,and undulators) and their spectral characteristics.

2) Diagram shows the features of a permanent-magnet insertion device and points out thedistinction between a wiggler and an undulator.

3) As the peak magnetic field increases, an undulatorrather quickly becomes a wiggler.

4) Drawing shows the mechanical structure that willbe generic for all ALS insertion devices.

5) The wiggler on Beamline 10 at tlm StanfordSynchrotron Radiation Laboratory was built byLBL and has many of the features that will be partof the ALS insertion devices. It has 16 periods oflength 12.85 cm and produces a peak field greaterthan 2 T.

6) Lombard _Street in San Francisco may be theworld's first and/or largest undulator.

91

Pole tips

Permanent magnets

Electronbeam

Photons

wiggler• non-sinusoidal orbits> harmonics• incoherent sum of intensities

undulator• sinusoidal orbit

• interference--> spatial and frequence bunching• coherent superposition

93

97

"_r, Jl rllllr' ' _1 _t

TECHNICAL CHALLENGE OF ALS

BEAMLINES

ALS

• Need to maintain photon source characteristics

in transport i_, high vacuum to experiments

• Photon delivery systems require

- mirrors

- focusing devices

- wavelength selection

• At these wavelengths

- refraction is negligible; lenses are useless

- efficient reflection only at 5mall glancing angles

° Therefore ALS optics based on glancing-incidenceoptical systems

• Also, development of microfabrication technique_permits

- diffractive structures, including "zone plates"

- multilayer for normal-incidence optics

• Power density can be severe

- several kilowatts/cm 2

• Optical elements must be cooled in high vacuum

- to dissipate power

- preserve surface quality to 5 microradians

98

ALS BEAMLINES

The following illustrations show:

1 ) Mirror designed and built at LBL to tolerate highfluxes of x-rays without thermal distortion.

2) The V[_ branch of Beamline 6 at SSRL, designedand built by LBL for high fluxes of wigglerradiation, contains many of the features plannedfor ALS insertion-device beamlines, including awater-cooled spherical-grating monochromator.

3) Proposed ALS beamline for x-ray imagingincludes the possibility of a vertically deflectedbeam that would illuminate an x-ray microscopewith a horizontal stage of the type biologists areused to.

99

ALS INSERTION DEVICES

Designation U means undulator; W means wiggler.The number is the length of the insertion-deviceperiod in centimeters. Undulators are about 4.5meters long; wigglers are about 2.2 meters long. Thefollowing figure shows the spectral coverage of theALS insertion devices and bend magnets.

1.03

XBL 893-5810

The ALS will produce bright beamswith undulators and wigglers, coveringa large spectral range.

104

The Advanced Light Source:

New Capabilities, New Research

ALS

, Next-Generation VUV Synchrotron Radiation FacilityOptimized for Insertion Devices

° Biological imaging

° INTENSITY, • Measurements on small or

"BR IGHTNESS" dilute samples

• Studies of ultrafast processes

"- • LASERLIKE COHERENCE

i • Studies of dynamic processesin biological systems

• SHORT PULSES (30_rilli3nths of a second)

• Bond_selective chemistly

• High-spatial-resolution

• TUNABILITY studiesi

• Lithography for chip

fabrication

Some "sci'entifi'cand"• echnoiogical areas that

will benefit:MATERIAL SCIENCES:THIN FILMS, SURFACESand INTERFACES

ELEMENT SENSITIVE BIOLOGY

CHEMICAL KINETICS andPHOTOCHEMISTRY

ATOMIC and MOLECULARSCIENCE

X-RAY LITHOGRAPHY andNANO STRUCTURETECHNOLOGY

t06

II I

J_ i,ll

I _t !_L-->-i T >

__-> _I!i]_:i , i_!!_ill->o_I :t_t I J • I.. _!i_i!?!

• _ _ ....................................................++-•...............I................................_ ;_ii__,_i_i_i__{"-/-- _t z .ii. i?ii_i'_i'-

!• • i

0

o "..C

_ F,"

t

107

SCIENTIFIC PROGRAM: ANTICIPATED EXPERIMENTS

ALS

U 8.0 8-(1000) eV _ chemistry and atomic physics

- high-resolution spectroscopy

- structure of actinides

U5.0 50-(1700) eV - materials and surface science

- high-resolution spectroscopy

- core-level spectroscopy

- surface EXAFS

- XANES

U3.9 170-(2100) eV - microscopy forlife and physicalsciences

- holography

- imaging

- structural biology

W13.6 1,000-20,000 eV - materials and life sciences

- small-crystal protein

crystallography

- surface EXAFS

- microbeam EXAFS

- atomic physics

Bend Magnets <1-10,000 eV - ultra-l_igh-resolutionspectroscopy

- variable polarization

experiments (e.g., circulardichreism in biological systems)

108

High-resolution measurements

High-resolution experiments are possible withspherical-grating monochromators

• recent result from BL-VI at SSRL

• resolution of 60 meV

_-- " T T _ T i ! i .,,. T T ,n

1.0-

- N20.8"

•_ _., C: -

(_

c: 0.6 - _ ls_ _ " -¢_, jl

0.4-

rr"

0.20.0 ' ! ' '400 401 402

Photon energy (eV)

x_ray absorption spectrum of gaseous molecularnitrogen, showing vibrational structure of ls-_"electronic transition

109

Element-specific imaging

• absorption.coefficient shows "edges"corresponding to photoelectron emission fromatomic shells

LLz

totalK

• contrast can be enhanced by measurementsabove and below the absorption _dge for aparticular element

• "water window" allows possibility of imagingbiological materials in aqueous medium

ii0

The ALS is well suited to chemistryand atomic physics

• undulator range:

- 6-10 eV lower limit

- 2.1 keV upper limit

o wiggler range

- to 20 keV

• bend magnet range

- infra-red to 10 keV

° short pulses for timing applications

113

PERIODIC TABLE OF THE ELEMENTSGROUP VillA

lA

,.=_. I IIA.. IliA IVA VA VIA VIIA

,ffi,O,F'L_' _ 'B_ 'C_ NeBe ,o.,,,,2.o1,,.o071,,.,,,,.,N ,o,,,=

"-=""' ' ' "P°"s'";:Na Geou, . i':il_lEl tSl i0=z.NI =4.sis 'lllD IVD VB VlB VIID ___________..VJ_VIII_19 lid n.N= _ =0.=74==.0,4=s._,s===.=u

ScI Ti I V IGr IMn FeiCo] Ni ICul Zn Ga As Se Br KrTil.riO410,1._O

sz.i©= 40.00 ,.t_l 4T.10Ilm.t4alltnllH.lS* a.e4:/lim.e_l] lm.T+I e_.=4I u_l ==.Tz ._,4.=nl'e_'''' sSlal44 (_-4S B]441 B4Y .... 1";11441_)4| O _Sl O i -[M--_0

"='RbSr" _'"Y" "Zr--_'"Nb_"Mo""Tc Ru Rl_ Pd Ag Cd ,!n ,SnISb Xe

M--WaZ W _H_ " El '_VlBIT' _ nll'_/lr rl_ lm o Po "At _qnCs=.Ba "La_ Ta Re es i_p_ r_i_u_ Rg, '_r_ Pb, _a, :" o,.,.,,,_=.4,.,mo.,,uro.m=,mu ,,,=_,,s.o_,,=.=,_,_.=71 =_.._.(=,o_(=,o)_=_

o"(ii)l_m®I'leelml ®Ii= O1== BIM elm _Io= _I=) ®Imm ei" _I_= BI_'k_I,,

;el Pr INdJPmlSml Eu IGdlTbl DyiHol Er lT ni Yb) Lu Icoo[ (CrymS=lStructure) _44).i=li40.amT!t4_J4| (t4T) ! imo.sm! l_=.msi tsT._ lisLe=Ntel.molts4.m=oll=_==lt_ ms41t_=.04i IT4.m_1

-=-- = --'- = ThIPa I U INPlPu)AmlCmlBkI Cf !EsIFm151 oc,_ (:::I _ 0 _.o_ (==l)1===.o_I (==_)I (=4=)i (=4=)| (=_) l (=4nI (=,m)1 (=M)..!(u_) ! (: ,m)! (=s_)I (=sn10,,-o,4o *_,*_ _ _*=*_'= 0 ,, , - - ' -- -

114

INSERTION-DEVICE TEAMS

Participating Research Teams will work with the ALSstaff to design, construct, commission, and operateexperimental facilities (insertion devices, beamlines,and end stations). In return for their effort, PRTs willgain privileged access to the facilities they helpdevelop. The following table lists the ix_ertion-devicePRTs that have been approved after an initial Call forProposals in March 1989.

115

_

=

ALS Insertion-Device Teams

Undulat0r SpokespersonsType and Alternates Science FocusU10 Tomas Baer (U. of N. Carolina) Chemical Dynamics (associated with

Yuan Lee (UC/LBL) the Combustion Dynamics FacilityAndy Kung (UC/LBL) initiative) '

U8 Denise Caldwell (U. of Central Atoms, Molecules, and Ions' J

Florida)Manfred Krause (Oak Ridge Nat.

Laboratory)Norm Edelstein (LBL)

U8 Vic Rehn (Naval Weapons Center-- Dynamical Studies of Materials .......China Lake

R. Stanley Williams (UCLA)Marshall Onellion (U. of Wisconsin)Richard Rosenberg (U. of Wisconsin)

Jory Yarmoff (UCR)U5 Steve Kevan (U. of Oregon) Materials Sciences (NSF Science and

Technology Center) ,,,

U5 Joachim St6hr (IBM Almaden Surface and Interface SciencesResearch Center)

Thomas Callcott (U. of Tenessee)

Franz Himpsel (IBM WatsonResearch Center)

David Ederer (NIST)U5 ' Brian Tonner (U. of Wisconsin) Surface and Interface Sciences;

Steve Kevan (U. of Oregon) Spectro-MicroscopyGiorgio Margaritondo (U. of

Wisconsin)

Marjorie Olmstead (UCB)U3.9 Steve Rothman (UCSF/LBL) X-Ray Imaging and X-Ray Optics for

Dave Attwood (LBL) the Life and Physical SciencesMalcolm Howells (LBL)Richard Freeman (AT&T)

Janos Kirz (Stony Brook)Wiggler Bernd Crasemann (U. ot Oregon) Atomic, Molecular, and Optical

13.6 Phil Ross (LBL) Physics with X-Rays; MaterialsDennis Lindle (NIST) Science

Chuck Fadley (U. of Hawaii)

Wiggler Alex Ouintanilha (LBL) Life Sciences13.6 S.-H. Kim (UCB/LBL)

Mel Klein (LBL)Linda Powers (Utah State Univ.)Steve Cramer (BNL)

116

Photoprocesses in Atoms, Molecules,and Ions

• Denise Caldwell and Manfred Krause: U8

• gas phase atomic physics with vuv photons

• proposed research areas:

- atomic structure through photoelectronspectroscopy, _ threshold photoelectronspectroscopy, fluorescence detection ofexcited-state ions

- electronic structure of the actinides

- structure of ions

• key participants:

Caldwell, Krause, Shirley, Samson, Baer,Lindle, Edelstein, Schlachter,, Morgan,Schneider, Prior

i

117

Atomic, Molecular, and Optical Physicswith X-Rays

d

• Bernd Crasemann and Dennis Lindle: W13.6

• interaction of x-rays with matter using 1-6 keV x-rays

- proposed research areas:c

- x-ray emission, x-ray scattering- photoelectron spectroscopy- Auger-electron spectroscopy- ion spectroscopy- absorption spectroscopy- visible/ultraviolet spectroscopy- theory

• key participants

Crasemann, Lindle, Jones, Johnson,Schlachter, Morgan, Prior, Schneider, DelGrande, Tirsall, Cowan, Deslattes, Perera,Krause, Carr, Brown, Kelley, Manson, Brion,Shirley, Bruch

118

Combustion Dynamics ResearchLaboratory

• chemical dynamics: U10

• Tomas Baer and Yuan Lee

• proposed facility: U10 undulator, IRFEL, visiblelasers

° research areas...

- photoionization, absorption, fluorescence- primary dissociation- molecular and metal clusters

- double and triple ionization- dynamics of excited states (pump-probe)- radicals and transient species

• key participants:

Baer, Lee, Kung, White, Berkowitz, Houston,Ruscic, Snyder, Hepburn, Moore

1

i

. 119

FURTHER INFORMATION ABOUTRESEARCH AT THE ALS

° ALS mailing list

* join or form research team (see me)

• ALS Handbook

* ALS Users' Meeting: August 23-24, 1990 at LBL

120

FRINGE BENEFIT

The scenic beauty and temperate climate of the SanFrancisco Bay Area come free of charge to thoseworking at the ALS. This January 1989 photo, takenfrom a hill behind the ALS, shows the brightly litconstruction site against the backdrop of a wintersunset.

121

122

_

RIKEN-JAERI 8-GEV Synchrotron Radiation Project - SPring'8 -

Yohko AWAYA

-The Institute of Physical and Chemical Research (RIKEN)

Wako, Saitama 351-01 Japan

Introduction

The plan of an 8-GEV synchrotron radiation facility, which is called

SPring-8(Super Photon Ring-8GeV), had been proposed by Science and

Tecnnology Agency (STA) in Japan and it was decided that its construction

would be started from April 1990. An atomic physics group in Japan had the

first meeting in December 1988 to discuss the future studies of atomic

physics and related problems at SPring,--8 and plans of research and

development(R&D) for them. Their report was published in May 1990.

In this report, an outline of SPring-8 is described. Results of the

discussions of Japanese working group of atomic physics and the present

status of R&D of this group will be presented by M. Kimura in this

workshop.

Requirements on SPrinqT8

Synchrotron radiation sources now available in Japan are shown in

Table I. In this Table KEK-AR is not a dedicated machine to synchrotron

radiation but the accumulation ritlg of the TRISTAN at National Institute

for High Energy Physics (KEK)° A next generation synchrotron radiation

source has been desired in Japan.

A joint team of JAERl(Japan Atomic Energy Research institute) and

RIKEN(R_!kagaku Kenkyusho:The Institute of Physical and Chemical Research),

both of which are supervised by STA, are now golng to design and construct

a high brilliant, widely tunable radiation source, SPring-8, in soft and

hard X-ray energy region at Harima Science Garden City in Hyougo prefec-

ture.

Brief history of this project is as follows:

1986' Design study of 6-GEV storage ring started at RIKEN

1987: R&D on accelerators started at RIKEN

123

,Jl_I _,r ' "' '11_ ' " ' " mP' "'

1988: R&D on accelerators star_ed at JAERI

JAERI-RIKEN Joint T_am was formed

R&D on optical elements started

1989: Advisory committee recommended to modify the project so that

I) the energy should be 8 GeV,

2) "long straight sections" should be prepared,

3) positron acceleration should be adopted.

Requirements on SPring-8 are

I) X-rays in the energy regior of about 1 to 25 keV as the fundamental

radiation from undulators and also high intensity X-rays with higher

energies,

2) brilliance around 1019 photons/s/mm?/mrad2/O.l%b.W.,

3) installation of as many insertion devices as possible,

4) wide tunability and high stability,

5) several "long straight sections".

In Fig. I, the spectral brilliance of this facility is given. SPring-

8 is forcused onthe shaded photon-energy-bril'liance region. In Fig. 2,

examples of estimation as to how wide range of photon energies is available

by changing the gap of undulators, lt is shown that at higher beam

energies, the range of photon energy becomes wider.

Advantages of "long straight sectlons", which is the most unique point

of SPring-8, are as follows:

I) longer insertion devices will be available so that higher brilliant

photon beams will be obtained.

2) several insertion devices will be installed at one section. Then at

the target position, wider tunability will be attained and also photons of

different energies will be simultaneously available if required,

3) it is useful to develop a free electron laser in soft X-ray region by

operating tile storage ring at lower beam energy.

Overview of SPrinqT_88

According to the requirements on SPring-8, specification of the

storage ring as a light source was aesigned so that

: I) the energy ef electrons/positrons is 8 GeV,

2) the storaged beam current is up to I00 mA,

: 124

3) the ernittance of the electron/positron beam is less than I0 nmrad,

4) the ring has four "long straight sections" as long as 30 m in addition

to standard 6.5-m ones. In the latter, the insertion devices of about 4-m

length can be installed whereas in the former those of more than 20-m

length can be done,

The storage ring consists of 48 cells and its circumference is 1436 m.

A unit cell is consisted of two bending(dipole) magnets of 0.67 T, ten

quadrupole magnets and seven sectupole magnets including a 6.5-m straight

section, as is shown in Fig.3. A lattice of Chasmann-Green type is

adopted. In every neighboring pair of cells, a high beta straight section

' and a low beta one are obtained. As a whole, the storage ring is operated

as ti_e 24-symmetric hybrid-type lattice.

The lon_ straight section was designed by replacing the one unlt cell

with a straight cell, which is attained by removing two magnets from the

unit cell(Fig. 4). At first, the storage ring will be operated under this

condition. After enough basic data are obtained, the quadrupole and

sectupole magnets in the straight cell are rearranged so as to get the

30.4-m straight section. The natural emittance of" the electron beams is

7.2xi0 -9 mrad when four straight cells are kept and Lhat of preliminary

-_ estimation is 8.5 x 10-9 mrad when four straight sections are achieved.

Principal parameters of storage ring are shown in Table II.

A I-GeV electron linear accelerator and an 8-GEV electron synchrotron

are constructed as an injector, Since the positrons will be storaged

finally, another electron linear accelerator for p, oduction of positrons isJ

prepared. Principal parameters of injectors are shown in Table III and the

concept of the facility is shown in Fig. 5.=,|

The characteristics of the electron beam and typical values of

brilliance and flux are shown in Tables IV and V.

The cite and buildings

o SPring-8 'is constructed in the "Harima Science Park City" in the

Nishi.-Harima (shown in Fig. 6) district which is being developed by the

government of Hyougo prefecture. The area of the cite for the SPring-8 is

141 ha. Since there are hills in this area, they will prepare plain areas

of 290-m and 280-m above sea level. In the former, the storage ring is

constructed and in the latter, the electron linac and the synchrotron. The

= 125

ground is firm (rock), so the facility will be affected little by earth-

quakes.

The layout of the buildings is shown in Fig, 7. The storage ring will

be constructed around the hill whose top is 345-m high above sea level.

Three 1000m-long beam lines and two groups of four 300m-long beam lines are

planed. The building for the storage ring and the experimental area are

being designed so that it is free from subsidence and vibratien of the

ground, not affected by the change of the atmosphere temperature and so

forth. In Fig. 8, plan of the storage ring building is shown. Outside of

the experimental hall, there are a passage and rooms for experimental

preparation. Cross section of the storage ring building is shown in Fig. 9.

Beam Lines and Scientific Proqrams

There are forty 6.5-m "standard" straight sections and four 30-m

"long" ones in the storage ring. Among the standard straight sections,

five low-beta sections are used for the installation of the cavities and a

high-beta section is used for the injection of electron beams. Then

fifteen standard low beta straight sections and nineteen standard high-beta

ones are available for insertion devices. Two of the long straight

sections will be for machine study and another two will be used by users.

Seventeen beam lines from the bending magnet are planed to be prepared at

present. Summary of the beam lines is shown in Table VI. Ten beam lines,

six from insertion devices and four from bending magnet, are planned to be

constructed when the first beam is obtained. Atomic physics group wants to

get one of these insertion device beam lines. The rest will be constructed

in the following several years.

The length of the beam lines is 80 m from the exit of the light

source. Since there is a possibility that the long beam lines are

required, the space for constructing the eight 300-m beam lines (four from

insertion devices and four from bending magnets) and three 1000-m beam

lines (two from insertion devices and one from bending magnet) is prepared.

One of each 300-m and lO00-m beam lines comes from the long straight

section. In Fig. 7, the beam lines marked by open circles come from the

insertion devices and others from the bending magnets.

The long beam lines will be used for the studies which require a wide

irradiation area or very low emittance photon beams. They will be also

126

useful when special large experimental equipments or special experimental

conditions are required ancl an independent building is prepared. At the

present, However, the construction of long beam lines are not included in

the first stage plan.

List of users' groups, which have been organized and are now making

their plans, is shown in Table VII. Ten users' groups(l-lO in Table VII)

are organized for special study-fields, five groups(ll-15) concerns with

new applications of X-ray scattering and absorption(ll-15) and six groups

(16-21) is classified by methods of measurements. Three groups(22-24) are

discussing the feasibility of photons in low energy region.

_n addition to R&D studies on optical elements and beam lines, R&D

studies will be done by seven users' groups of special study-fields

including atomic physics in FY 1990. The atomic physics group will study

control-techniques of multiply charged ions, mainly transportation and

trapping of ions

Time Schedule and Total Budget

The construction of SPring-8 starts in F¥1990 and commissioning is

expected in 1997. Facilities will be open for experiments in 1998. Budget

estimated in 1989 is 108.9 billion yen for machine, buildings, utilities

and ten beam lines.

- 127

'_r_

"T--

- _ ,,- ,,- ,... ,,-"0 _ "0 "0 "_ "-" _ _ :t_ :t4r.

C:: C _ _ :_ _ U..' la_ 't..t, la, L._ LL.._:Z) ZZ) _ _ :) rn __, n_ r, n 1::9.. n n_

e

ii o

I o,

| o.

! 0

.. . .... . ,

L_,:_:.". " _'-' _',_;_; "__.,',..;_ ,_-_/, t :,'_"

._':q,.. _1', _..';.-,,¢:__,_,_.__,:., }:" _.:;_'d._:,,"_,•. ,_.., , _.,.-1;_._ r,, . ._., •• I:::•- ,....:_.-_-; -.,,t,_._:,_,u,: r._,_,'_nap¢.._.,_,._p__':,,M.@. ,,-.., _....,,,_"'-

....._ ,_:_':.L: ._.:'; "__V".:E ....... z_r_'" ...... ,_.., ..... . ....o

";'," ;'.".i_:,'.',-_;''_,_'_..,'.':"_d :_",.¢'_' I F 1_ I ,,," i _ _ 0

© = ,ii.': _, __,__,*_,,. t , ,..."' .,"'.' I.._'_, I.._:!,,._.:,._.:_.. :@4, [_ I,o _. t

.....,'.,; , ','::',.,.:.... ._....._..-,. .; _,_., _ _ %,%

©I

_._ o _ co r-.. t.o u_ ",:r co oj ,.-. o '-

C:) C> 0 0 0 0 C:> C:> 0 0 0

•_" q o/oL'O/_;pe_ m/_; tu tu/s/su o_o q d

129

Undulator 3cre120 I

I100 .... I ----_'_"__ ....... --_ 6 GEV(1)

, ....... S'_

•,-- "4- 7 GeV(l):>--m 8 GEV(1)

-_ _e- 6 GEV(3)"_ 80 ....... . .__ -ll- 7 GEV(3)

_- /f _ 8GEV(3)r-- "_ 6 GEV(5)

,--_ 60 . - ...z_._mmo4_ ..... -_- 7 GeVC5-')O .-In- 8 GeV(b')o

4O

20 ,i,

0 _ ....0 10 20 30

gap length(mm)

Undulator 4cm80

-e- 6 GeV(l)

_- 60 -4- 7 GEV(1)

.4- 6 GEV(3)

-c_ 8 GEV(3)

40 , -_- 6 GEV(5)

O "_ 8 GEV(5)

0 "" I 1 1 ,

0 10 20 30

gap length(mm)

Fig, 2,

130

o

otD

131

i SPring-8iL

Fig, 5,

IBB_

>

©

135

-

c_c_ c_c_

_c_ c_c_ c_c_

0

R

" E

. _ __, g_"" . _>__

136

Table V,

Typical Values of Brilliance and Flux

Brilliance Flux

Devices (photons/sec (photons/sec

/m rad2/O.1%bw) /0.1%bw)

Undulator 1 2.0x1019 1.4x1014

Undulator 2 1.5x10 20 7.3x1014

Wiggler 1.6x1018 2.8x1014/mrad

Bending M. 2.3x1015 1.3x1013/mrad

Undulator 1: Xu=3.3 cm, L=5 m, K=I, E0= 12.3 keV

Undulator 2: ;Lu=3.3cm, L=30 m, K=I, E0=12.3 keV

Wiggler: Xu=18 cm, [.=2 m, K=25, E0=63.9 keV

Flux: Flux through a pin hole

(_ = _ =1.0; _, e=6.4 Brad)

t37

T ukuba.

ashi o( K,ETL,SORTEC)eo Tok,

r

Harima Science G; ty _ = ,O

Okazaki

0 (IMS)

Fig,6,

138

Table VII, List of Specialist Groups for SPring-8

1. Surface and Interface2. Extreme Environment3. Phase Transition

4. Electronic Prope .rty of Solids5. Chemical Reaction (Chemical Crystallo_aphy)6. Atomic Physics7. Protein Crystallography8. Macromoiecular Solution and Muscle9. Medical Application and Diagnosis10. Actinoids11. Nuclear Excitation12. Nuclear Resonance Scattering13. Ma_etic Scattering14. Inelastic Scattering15. Photoacoustic Spectroscopy16. XAFS17. Topogaphy18. Diffuse Scatte_ng19. Extremely Small Scattering20. Trace Microanalysis21. Soft X-rays (Microscopy)22. Soft X-rays (Photochemistry)23. Soft X-rays (Solid State Physics)24. Infrared Spectroscopy

143

Photoionisation of Ions _nd the General Program in Atomic and Molecular,Physics at Daresbury

J B West, Daresbury Laboratory, Warrington WA4 4AD, UK

To date the only cross section measurements made on atomic ions o'iginatefrom the joint programme between Newcastle University and DaresburyLaboratory a few years ago. Yet from the theoretical viewpoint, and for anunderstanding of loss and confinement processes in, for example, fusionreactors, they are in great demand. The problem lies in obtaining a wellquantified atomic ion beam, of sufficient density that the photon flux willallow reliable m,easurementsto be made. For calcium, strontium, barium,zinc, gallium and potassium ions this was achieved at the Daresbury SRSusing a merged beam technique, where a well collimated light beam wasmerged over a length of about 10cms with the ion beam as shown on figure 1.

' 0

Figure 1 (For an explanatlon of the symbols, see Lyon et al[l])

._.1 11I I1 _ rlil , l't,i

--r- , , _ Figure 2, taken from Lyon et al[l] wherethe experimental procedure is also

nI t described, shows the precision obtainablefor Ba+ in the region of the Sp- 5d

_I resonance Absolute cross sections with an11 -

II accuracy of --_+12%were obtained, where

t! ali the absorbed photon resulted inenergy,, I the production of the doubly charged ion.

"; It'... { Tlne technique could meas,,re cross• { I sections down to -..10"17cm2, assuming an" I f /k! incident photon flux of 1012photonslsec,

I ,} /i \ and this limitation prevented useful

[ _ 4¢/t \, quantitative measurements being made on\ other singly charged ions.I k,

.; ".,.. With only minor adaptation, this equipmen_

I 1 I could be used to detect higher charge

Figure 2 Total cross section of Ba+ in the region of the 5p - 5d resonance

144

states resulting,from the ionisation of singly charged ions, with the interestnow moving to ionisation of deeper inner shells and core levels. Aparticularly interesting case is magnesium, an important element in stellaratmospheres and tractable theoretically. However, this means partitioning ofthe cross section since higher multiply charged states are accessible, withconsequent lower count rates in any one channel. For this reason a photonflux in the region of 1014photons/sec is required in the grazing incidenceregion of the spectrum; the monochromator output must be substantially freefrom higher orders and stray light, and this implies low efficiency. This isbeyond the capability of today's conventional storage rings and will have toawait the very high intensities available from a source such as the APS.

The current programme in Atomic and Molecular Science is focussed onphotoionisation of atoms and small molecules. On the atomic side,experiments on the double ionisation of helium were completed recently[2],verifying the Wannier thresl"old law for double photoionisation. Also, theangular distribution of the electrons has just been measured, and theseresults show a marked divergence from theoretical expectations. Otherexperiments include fluorescence polarisation measurements for the atomicions calcium and strontium, which, when combined with photoelectronangular distribution measurements, form the complete photoionisationexperiment. A sizeable part of our programme is devoted to studyingmolecular fragmentation. The triple coincidence technique, in which the twofragment ions are detected in coincidence with the photoelectron after tileparent molecule has been doubly ionised, was developed at Daresbury[3], andexperiments in this area continue with the addition of fluorescencemeasurements.

Photoelectron spectroscopy continues to be used as a basic technique;prominent among experiments in this area is the joint NIST/ANWDL project,using a high resolution angle resolving system shown on figure 3.

This system, designedand built in the USA, hasbeen fitted to the highresolution 5-metrenormal incidencemonochromator at the

C 'le

"' ""' _ Daresbury SRS andL

"" _c = produced precision,,,_ _'" bench-markmeasurements on a

o, _,,,,,,,.,_ number of small_.1 O_ _m_:f_'vaqrtet-I Ir_4_l£S'I Lrkrc'tr_ _(trqm_te-I II=NI

__t.

FT _ hrmmt'm _'_d_.n

1

Figure 3

145

- _

Figure 4 shows the angular distribution parameter for the v=l vibrationalmember of the N2+ X state, in the region of complex autoionising structure.

The assignments shown are derived from earlier experimental work and mayhave to be changed as a result of these measurements and recent theoreticalcalculations; full details are contained in West et al[4].

z.o- Precision

ta measurements have,,., also been made on the

1.6 _., _I, molecules 002 and H2.• _ _,Z Pl71

tL. _ I _- i ,,.*'_ 1 '"' The data for CO2 are

II c,,., '" being analysed

" 1.0, [I}_,-._ _ ',l'i _4o ,,,o '.,._JT" t.,.z3 _"_ Iz _,,.zJ,, i _ 7._,/ _ assuming three

=" ,/ _1 c,,.oJ'_I [ Jll vibrational modes arei ,._'_ I l , ,,_ 1_,, present: symmetric

, stretch,

0J, ,i _ _'_l't"J_t/l__', _t1_t '_t antisymmetric stretcho.: _ i and bending, and theo.0 ,, ,,,.,-- data set for this

15.9 16.0 16'.1 1(_,2 16.3 16,& 16.5 16.6 l&'/ molecule covers the

Phat'on _nerg,/ (eV} ionisation region from

Figure 4 The angular distribution parameter for the v=l member of the

ground state of N2+.

"t the X-state threshold to beyond the- B-state ionisation potential on a..i photon energy mesh of 2meV. Figure

ii t 5 shows a comparison betweenresonant and non resonant

_.t ]l_j_l behaviour, where the photoelectront spectra indicate the presence of." I _..---- .,L......._..___._._.....__ higher vibrational modes for the' ....... " resonant case.

-. In tiqecase of the H2 experiment,"" angular distribution measurements

,- were made in regions where_" vibrational autoionisation takes

i ,." place, close to the thresholds of

- the rotationally split H2+

i i .__---_ _L [ vibrational continua. By this means-_----- I rotational infcrmation can be, _-

................. obtained, without the requirement

Figure 5 "On" and "off" resonance CO2 photoelectron spectra.

for rotational resolution in the electron spectrometer. There have long been

146

theoretical predictions for this effect, and confirmation has had to ,waituntil now for an experiment with sufficient precision.

Looking to the future, the atomic and molecular science programme atDaresbury will move closer to applied science areas, with metal c!usters andtransient species becoming more prominent. Much of this work will require a

source with two to three orders of magnitude advantag_ in photon intensity

over the SRS, and a design study is presently unGer way for a VUV/Soft X-raysource to meet these requirements.

References

[1] I C Lyon, B Peart, J B West and K Dolder J Phys B19, 4137 (1986)

[2] G C King, M Zubek, P M Ru_er, F H Read, A A MacDowell, J B Wes_ and

D M P Holland J Phys B21, L403 (1988)

[3] L J Frasinski, M Stankiewicz, K J Randall, P A Hatherley and K CodlingJ Phys B19, L819 (1986)

[4] J B West, M A Hayes, A C Parr, J E Hardis, S H Southworth, T A Ferret't.

J L Dehmer, X-M Hu and G V Ua_r Physica Scripta (in press)

147

Research with Stored Multi-Charged lons at the APS and the NSLS

Churchl,*'_ _ I 2 2_. D. _ravis, B. M. _ohnson2, M. Meron , K._W. Jones ,D. A.

I. A. Sellin_,_J. Levin-, R. T. Short-, Y. Asuma4, N. Mansour-, H. G. Berry-,: and M. Druetta b

•Invited speakerI. Physics Department, Texas A&M University

: 2. Brookhaven National Laboratory3. University of Tennessee and Oak Ridge National Laboratory4. Argonne National Laboratory5. University of St. Etienne, St. Etienne, France

ABSTRACt

Potential ion beam and stored ion t&rgets for research using synchrotron

radiation from the Advance Photon Source are discussed. The difficulties of

cross section measurements for the photoionization of ions with high charge q

and atomic numler Z are mentioned, but preliminary observations of photoionization

of stored Ar2+ and Xeq+ (4 _ q _ i0) are described, and a brief discussion of

•the measurement technique is nresented, with reference to improvements possible

usir_ undulator and wiggler radiation frcm the APS.

Earlier presentations at this workshon have nrovided extensive motivations

for research on multi-charzed ions, among other targets, using synchrotron

madiation from the Advanced _oton Source. We note only that charge state

distributions re_sultin_from vacancy cascades following inner shell photoionization

_,_atoms have be_en studied only for a few ta_]_ets,while similar

v_cancy cascades Ln ionic ta_ets bravenct been experimentally addressed at all.

However, some caiculazions for -he ions cf iron have been carried out. To study

such systems, and to measure cross secticns for the nhotoionization of ions, dense

ionic targets 'mirha range of charze states c emd atomic number Z are desirable.

Among the most iLk.elycandidates are_a ccntinuous ion beam from an Electron

©yclotrnn Resonance (ECR) ion scurce, and ions ccnfLned in an ion trap. ECR sources

have pr<duced be_mnswith charge states as high as _r16+ and with beam currentsQ+

exceedLng I00 micro_mperes for _r _ . Thus, mon densities near 106/cre3 are feasible

with typical source parameters such as a !0 mm diameter apertume, I00 mm-mrad

emittar:ce,and !0 ,.7extraction. Significant imnrovements in ion densities

would be possible, if tighter beam focussLng were to become feasible. (lt is

assumed here that a beam waist ccmnarable to the diameter of the source aperture

-- _ _ _'_7_I _m_7_I_. ]

]48

Alternatively, a Penning trap cmn he used to hold ion targets produced by

electron impact, photoionization of neutrals, or other means. Preliminary

analysis of results from measurements at the NSLS, intended to demonstrate the

photoionization of ions by this method, are now nresented. _lotons from

unmonochromatized bending magnet radiation from the NSLS were focussed near the

trap center by a cylindrical mirror with 4 mrad horizontal acceptance. The

photon bemn was blocked by a fast shutter, as needed. The "white" radiation

was filtered only by a Be windon before the trap. The transmitted beam flux

was monitored with an ion chamber.

lons stored in the trap were detected on a charge/mss ratio basis by

resonance absorption of rf enerzy by the axial oscillation frequencies of the

. Ar 2+stored ions For mea_nmrementswith an target, electron impact ionization

of a "puff" of argon gas into the trap vol<_e f_n a fast valve was used.

The ions were stored for two seconds_ to permit the target gas to be largely

" pumped away, and then a pulse of synchrotron radiation irradiated the stored ion

target. The resulting ion si_nals were detected, and the ion sample dumped

preparator%'to background measurements. Background ions arose from two sources'

one was stored ions other than Ar 2+ produced by the electrons, and the other was

photoionis produced by ionization of the residual target gas. These backg_rounds

were removed by two cycles similar _o the "signal" cycle just described. In the °

second cycle, no electron pulse was used, yielding the back4_roundphoton signal,

since no targ_etions were present. In the thimd cycle, no photon pulse was

employed, yielding the background from the electron pulse, since no photoionis were

produced. The multi-charged argon ions remaL]ing alternsubtraction of these two

backgrounds were interpreted as the net signal from the Ar2= photoionization. The

average of a nmnher of these triple cycles yielded a net multi-charged ion signal,

with a peak height distribution significantly different from the distribution

t-ypicallyobserved when photoionizing atoms.

The successive photoionization of stored Xeq_ ions was s_died in a similar

manner, but in this case synchrotron radiation was used to nroduce the sot-redion

tarzet, as well as to ionize it. In these measurements the photoionization of

residual Xe atoms durimg the part of the cycle cycle followir_ the gas puff

prodtJcedmost of the bao_kground, in a distribution of charge states. A net signal

of highly charged ;<eions was found. In these measurements, target densities ne_m_

107/cm3 for _r2+ and 5 x I05/¢_n3 for the Xenon ion target were estimated

-

i49

_

In conclusion, net ion signals from measurements designed to observe

the photoionization of ions stored in a Penning trap have "been observed: With the

_creased flux of synchrotron photons potentially available from an }hnS

wiggler or undulator, both ion target densities and photoionization rates for

the stored ions should be increased by an order of mangitude or more. A band-

width of 10% is provided by the unfilted undulator r'adiation, which .nan be

reduced to about 2 % b y a pJJlnole paerture, is also attractive. Since ion

densities similar to those in the traD are available from ECR beams, and sit,ce

particle counting is available without the trap magnetic field (which will

increase the sensitivity over the analog detection by a factor of 143 or so), rbe

future of photoionization studies on ions cannot be dismissed.

150

Multi-Charged Ion Research Using theAdvanced Photon Source

/ • I lIJL1_l ILIC;]LI I I_.,_(;;_ILI %,*I I /-Ikl I_'C;;IL,_._

2. APS beam properties and ionic targets

3. Photoionization of ions at the NSLS

151

M5

M4MsM2M1

E3

L2

LI

K

KrFig. 1. Typical example of the vacancy cascade for

filling the initial K-shell vacancy of Kratom. The solid circle indicates the electron

and the open circle represents the vacancy.Arrows show the direction of the vacancycascade.

Table I. Relative abundance of ions resulting from an inner-shell

vacancy of Ar atom with and without electron shakeof[.

K La Lt L=Charge

A B A B A B A B_

I 0.7 0.9 0 0 0 0 0 0

2 8.6 11,2 3.7 4.4 85.0 100.0 85.1, 100,0

3 10.3 10.3 82.5 95.6 14.8 0 14. 8 0

4 43.2 53. 1 13.6 0 0. 2 0 0. 1 0

5 26.1 18.6 0,2 0 0 0 0 0

6 9.3 5.9 0 0 0 0 0 0

7 1.6 0 0 0 0 0 0 0

8 0.2 0 0 0 0 0 0 0

A : With shakeoff.

B : Without shakeoff.

( 376 )

Bulletin of the Institute for Chemical Research,Kyoto University f_., 373 (1985)

152

From Phys. Rev. A .3._4_,216 (1986)

28 I I 1 I I I I I.....

24

3p4

3p

0- 0 4 8 12 16 20 24

INITIAL CHARGE Zi

FIG. 2. The mean final charges (Zr)resulting from the cas-cade decay of single inner-shell vacancies which can be createdin the various nl subshells of iron ions with initial charge Zi.

153

MULTI-CHARGED ION TARGETS

(1) Ion beam from ECR ion source

Example: PIIECR @ ANL

601_A Ar8+ beam at 10kV x q

Assume crossed beam geometry,focus to 1 cm diameter spot

Then n = 106 ions/cm3

(2) Ion trap

Stored densities of cool, singly-chargedions = 107/cm3

... expect n = 107/q ions/cm3 at best

154

ECR Source

Assumed emittance = 100 mm mradSource diameter = 10 mm

BEAM WAIST10mm

ION _ ' 20mmBEAM

dL. 1m --,i-"

=. 106/cm 3 for 501_Aof Ar9+nmax

Undulator A beam spot @ 60 m from ring = 2 mm x 0.75 mm

Wiggler A beam spot @ 60 m = 120 mm x 0.75 mm= (2 mrad horizontal)

- Wiggler A, unfocussed, with 0.25 mrad horizontal fan ofradiation, in = 4 keV bandwidth --> = 3 x 1016 photons/s

Undulator A, 10% bandwidth --->= 2 x 1016 photons/s

Undulator A, 2% bandwidth with pinhole --> = 2 x 1015 photons/s

=

155

iii0 i,,,,

• / (..4"" .-'"_L.'# .-" °•' . S X

• i ,./_ /. =!//;

• ti .'i! ':°,,J S I

: II i Iii-;ii l i o

, " , , o,l ; t u

,. .i < >_ t"i , E' ; ' I i

' , I _-_'o '_ c_

' ' I << E El._''ii I _ "_ii ' E_°o°>", | I2_ i,.I

.{:1' °° ° -i", ' "" "" <"

', I >> £5_ _i <

1 I I"- _'-,, ""_ _, t _._.__ x - ,

I"l 0..

i t <<Oco' t i

. : , I I ¢1 iii|

i I I I : , iii' : ' i I O_ I._: ii ._ :)

' i, :1 : , , I :lo

ti l ' <,,: ' li o _

..... l, I !, _i,,__...... ,i,..}iilil I i ! |is. ii ! • • |lliil i . I i |iilll i i ii_ |11111 1 I • _ _

lx_ _ L'_ 04 _ -0 ' _ 1,,,

0 {:_ 0 C:) 0 0 <:D _ u

(P_X_/A&H%['O/s/qd) xnL4 =0

o

156

Photoionization cross sections at K edge

(1 0-20 cm2/atom)

Argon Z=18 EK=3.2 keV _K=7.2

Cu Z=29 EK=9 keV (_K=1.6

Ze Z=40 EK=I 8 keV _K=0.43

S n Z=50 EK=29.2 keV _K=0.17

W Z=74 EK=70 keV _K=0.05

From Storm & Israel, Nuclear Data Tables AI, 565 (1970)

157=

1618- u-

o4 2 -EO

ZOF-o 1619--UJ0")

rf)cD0Eli0 5--

10-20 I I ! I . I1 2 5 10 20 50

PHOTONENERGY(KEV)

t58

Ion confinement, photoionization of ions, and low energymulti-charged ion collisions at X-26C, NSLS

Scott Knavis, D. Church Texas A&M

B. Johnson, M. Meron, K. Jones BNL

I. Sellin, J. Levin, R. Short ORNL/U. Tenn.

Y. Azuma, N. Mansour, G. Berry ANL

Michel Drvetta Lyon and St. Etienne,France

160

ION MOTION IN A PENN_G TRAP

2 qVo

_z mZ2o

= qB,C mc

Wc ]_2 2_C = __+ C _ Z' 2 4 2

_C W2C ZWm= "-2- -4--T

B2Z2m o

Stability: q < 2V

161

ION-TRAP_[ i

, ,iii

FI,A E.TL ......... CO.TROL-,, , , --- _ ..... ELECTRODES

-.

' ._ Zo_-Ro _RIN G

-- - END- CAP

......... - ................... - DECELE RATORi

COLLECTOR

ilill i

| -------,!

1 cm

- 162

_

___ °dwno r,.

_ Lr) _)

-- 0

S±NflO9 _ OI164

<:I:

ed --- 0S_LNNO0 OI

165

_

iilili t J iiliiii_ _ iiJl,I, r', ii t i ii,J,_ i , iiilili, i

L©_ _

g i -_ c_ C_20 _'_ - -

m 'C _ L_

0

B _ _ _ _

_._ - _ _,_

® _.

e _

_ -

C_ - -- _

-_ - - c,J

_ '_ IlI|l I I I Itlttt I I ,,,, I,_,11 l,!| , ] ...... J I ..... I,,

. .- ........... __..+_.... .- ....... : ...... _ : ,,,, , ,

166

_8.

ION TRAP

t B_,_'--- ,Zo )/

bm

TRAP RINGELECTRODES

_. SWEPT 7/+

', T EXCITATIONIr,

" I -- {_) I I+DETECTION_

167

" 2l-

10-18

"WHITE LIGHT"5

10-2o1 2 5 10 20

PHOTONENERGY(keV)

170

Ion Production

G - ]'Ek _(E)F(E)dE

a(E) - photoionizationcrosssection(K she11)

- F(E)dE = number of photons/s through the trap in energyintervaldE

For NSLS, with 70 mA in the ring, G _- 10 -5 cm2/s for"white" bending magnet radiation on Ar.

171

ii, 2 ,x 107 / cm35 x10 5 / cm3 --

>. _-•-- 0

ZOO --uJOz a-" LU

Q- _ '

I I ' J i Iro 0 ' ro ro 0 ro

RadialPosition RadialPositionXeq+ Ions Ar2+ Ions

I

__

I

PHOTONS PHOTONS

173

0CD

C:_

_-- iJJ 1.1.1--J _JO, 0

r-7 r'7--- z z

_.J0 0

Z rr" O2

>-- o9 0 0

t.u o3 rncD

mm

174

T.

' _lri, _ll I ....... ,llp,,lll ,.... I1,'_,' _,' III ' ' ll_l'_'l ' ' I_f 'Ill'rill"

INNERSHELLPHOTOIONIZATIONOi- Ar2+PRELIMINARYANALYSIS

TOTALSIGNAL-BACKGROUND1 ....

r 1 :

" : .... --_,T_L.L-L--

SIGNAL-BACKGROUND1

SIGNAL- BACKGROUND2

Ar4+ Ar5+ Ar6+ + +. H3 H2, .-/T,x_y?_ .._,._-_,_

12 10 8 6 4 2

-q_--- M / Q

i

176

l],n,t

I

I0

5

o0 2 4 6 8 lO 12 14

*Adapted from Mukoyama,J. Phys. Soc. Japan .5_5.,3054 (1986)

4

: 177i

q+SEQUENTIALPHOTOIONIZATIONOFSTOREDXe IONS

PRELIMINARYANALYSIS

SIGNAL-BAOKGROUND1

SIGNAL-BACKGROUND2

12 10 8 6 5 4.__--_ Q

- 1.78

,_ ,Ill,,klllldl_l, _d_J,,

1.80

181-

_

Storing an lon Gas --Why?

1 precision........ -_

(1) Tstorage - Ar spectroscopy

-_ Study metastable levels.Also, T Storage

(2) Same ions may be targets for different beams, or repetitiveinteractions with same beam "_ prepare particular states of

ions (optical pumping).

(3) Low ion energy * study collisions diffic_tlt to do withbean,s; also small cross-sections, e.g. dissociativerecombination ion-atom reactions.

(4) Weak, well-defined interactions witI_ neutral (or charged)beams, e.g. photodetachment of stored negative ions.

182

"ltmughts on Future ESSR Studit,,"sof Inner Ck_re Levels|

M, O. Krause

Oak Ridge National LaboratoryOak Ridge, Tennessee 37831-6201

Mu,.:h of the research I see to be done lit a tumtble laigh-brigtatncss, high-energy phc_t_)taSt_ul'cC

cltn t_tkc Its _l starting point w_rk done in the past, some in the distant plist, s_me in the recent p_sl,

but illmost always rudiment_try or explc_ratory in torture, lt began in the mid-twenties when Pierre

Auger _bservcd various tracks in a Wilson Cloud Chanaber filled with a rare gas and irradintcd by

energetic x rws. _ As seen in Fig. 1 there were long tracks, whose lengths changed with the hlirdlacss

of the x rays _nd shorter tracks thi|t always had the slime length for a given gas and originated t'ronl

the salrle spot as the lc>rig tr_:icks. Now-a-days wt: show this photogral'_hic pllltc Its evidence for the

experimental discovery of the rndiationlcss process of atomic de-excitation, the Auger I:!l'l'ect -- la¢_doubt

true; but these plates also served the important purpose of determining the angular distributic_ns o1' the

plaotoclcctrcms, actually the primary goltl at the outset of Auger's thesis. Todi% I show this plate as

an illustnttion of electron spectroscopy which at its very beginning used x rays of high energies lying

in the rc.gime tc, he covered by the APS, and sources such as PEP, ESRF and SPring 8.

Let's l'irst look at the Auger electrons in this discussion ot' future ESSR studies (I.:.lectrc_n

Spcctr(_mett T with Synchrotron Radiation) 2 By now we have a rather good record _1"Auger spectra

associated with K shell ionization. This knowledge comes primarily from studies with atoms undergoing

nuclear conversion, il'Z is high, and electron- or photo-excitation, it'Z is low. Wc also have a good

general, and often detailed, knowledge ot" Auger spectra arising from shltllow mrc levels, again t'mm

elcctn_n- and ' x'photo-excitation." However, as sketched in Fig. 2, there is an intermediate regimeno1'core

levels and Z where data are very scarce because of the lack of x-ray lines of suitable energies. This is

an area where a strong tunable photon source in the i() to 100 kev range could fill the g_lp. 'l'hcn a-

= rlurnbcr ot" biisic questions thai still await close experimental scrutiny can also be addressed. Among

them arc (i) a test of the Breit lind Lamb shift terms over a wider Z range by way _1' the KL_L_

__ ciae@es in heavy elements and (ii) an accurate delineation and extensive survey c_t'the coi'rclltl/on

c.lTccts dcmlim|ting Coster-Kronig transitions originating in not only the L_ subshell but al_;c_in the M_

and N_ subshclls of the higher Z elements and, ii' energetically allowed, the L,, M_,, N,, ctc. levels.

Dcterminatkms _f Auger and photoelectron energies, line or level widths and transition prol_abilities

nrc required to probe the correlations and test predictions of advanced the{)ry.'*

I.ct's now l_x_kat the Coster-Kronig (CK) transitkms. Ckmsider Yb(Z=70), w,ith E(I_) -- 10.5 keV,

- E(I,,) = 1() keV, i|nd E(I_.0 = 8.9 keV. An L._Auger spectrum (or x-ray spectrum) v,'_uld be pr_xtucc¢t

"Th_ m_m,tleO mnnu_ript hns been

183 autho,_ by n contrsctor of the U,S,Government under contrnct No, DEACOS-.84OR214OO. Accocdingiy, the U.S,Govecnrnent ¢et_,rm a rwor_xclusive,

-- royalty-free _en_e to publish or reproducethe pub_shed loom ot this contribution, or

- allow others to do so, fo¢ U,S, Govemrnent

.... ' jl_i,J,!Jl_,,,illlk

P.Auger (1925)

p.

Wilson Cloud Chamber

Figure 1 Photoelectron and Auger E]ectron Tracks

of Argon excited by W X-rays.

"_ ,tJ_e z. lO .te- _,O .to _t_ _0 [,_ -IoO

) I'I - -- x 0

_ (o)

x. cove,,,,( j C_ l_,_'Jry c, vt,,,,,_, 0 v.<,v,.,,¢

Fi gure 2

184

with photons of 8.9 < hu < 10 keV; _ln Lz spectrum and _t I,:_ spectrum c(_nt_lining C.¢_ster-Krc_nig

satellites plus tile I.,.,I_,_XCoster Kronig spectrum would _lrise l'rom excitlition between 1().() < hu < 1().5

keV, Suit_d'_le comp_risons of these spectra will then give the Coster-Kronig yich.t for the I.e level.

Similar considcr_ttions _tptily to the detcrnlirlntion ol' the i,_ CK yield and it sh_uh.l I've m_ted th_tt these

rnensurements.could Ive c_lrried out with phc_t(ms as they emerge t'r¢_m nn undulntc_r withc_ut the need

o1' further nnrmwing the phc_ton distrihuticm. Howcw,'r, ii' we were to determine the CK raltcs by waly

ot' the I_,,_lnd L._le_,el wMlha', mcmochrom_ttic x ruys would be required, nnd the resc_luti¢m shc)uld be I P

better than 1()% ot" the natural line width (F(L0 = 4.60 eV) tc_achieve nccurate results. N_rr¢_w-b_tnd

x rays nrc nls(_ needed it' the photoelectrons _lre utilized l't)r the deduction _1' line widths _nd yields.

In the most s<_phisticated _tnd cleanest _pproach, coincidences between t_holt_elcctrt_ns _nd Auger

electrons (or x rays) are used tc_ meusure these parameters _nd, mc_st signil'ic;_ntly, ol_tnin inl'orm_ti¢_n

(_n Auger processes in _ttonls doubly ic)nized in inner shells. F'ig. 3 shows _tn cx_lmple l'¢_rl_h_t_i_nizn-

ti_n in the Cu Le suhshell, s While in a normi_l (nonc_incident) Auger spectrum the L, _nd I._ grc_ups

_nd their respective satellites overlap strongly, coincidence with the l_,ephot(_electr¢_n selects twt_ gl'_ups:

the n¢_rm_l I-,e M._.s"and the satellite group L._M.,.s arising from _ vncancy transfer I,, -_, I., in a CK

trnnsiti<m. This pilot cxperin_ent cin Cu clearly demonstrates the benefits theft ,,,,,illnccruc when it will

become l'e_sihle tc) dilTerentiate in coirmidencc experiments the ctec_y pr¢_ccsses in the I. suhshells as

well as in the M and N subshells thrc_ughout the periodic t_d_le. In additi(_n tc_the CK satellites _t' Fig.

3, other groups ¢H's_tcllitcs _ppe;tr in Auger spectra _s a result o1' shakeul-_ an¢] shnkeotT in the initinl

ionization process (with the term "shrike" used gencricly).

The shake process has _t c¢)untcrpart in the photoelecm_n spectrum as sh(_wn in Fig. 4 t'¢_rArg¢_n.

E',idcntly, one wc_uld like to resolve the sh_keup lines and sep_trate them l'mm the shakeolT c¢_ntinuum.

What one would hope to achieve is an improvement in the spectral qt,_tlity as h_ts ¢)ccurred already with

the use ot' an undul_tor source _t very low photon energy, see Fig. 5. For the K shell, this rc.quires _._

phi)ton he_ml with an energy spread ot" better than the 0.68 eV of the Ar K level width _nd a sutTicicnt

llux to compensate for the tenuity of the atomic target. Similar experiments that _rc limited only by

the natural width barrier" will become t'easihlc for higher Z elements and a vt_riety of suhshells with the

mc)rc p¢)werl'ul photon sources ctnd will allow us to hetter understand the double pll(HoelTect and its

dependence on the photon energy.

Remaining with K shell ionization in _trgon, 1 like tc) show with the aid of I:ig. 6, h¢_w the sl_ke

pr¢_ccss reveals itself in distinct satellite groups in the K Auger spectrum. These satellites have been

exploited 7 to delineate the energy dependence of shakeup and shake()l'f, respectively (see Fig. 7).=

- 185

ORill.Oi_ 61i,_ililll

ORNL-OWO 80-¢5940 ArK (IlK) ll._06eV +

' _ h,,,, _#,s_,zV i1 I _t 7;/_ :

I

600_ ........C;uLz

1 i

/ , '°+'_'I°__'+_tll" t. ,,,M,,i,_-__ Li+-Mi_, _: ,m",oi----COmm-.I:mENTARY.... /-I-----'I--I ..........., SHAKEOrF / i BOUNO I + I

' I J-I'"'"M+ I_ ' 1 11.,3p-4o I I: +ooi...._ i "I ..t\" r--I........

o= i ,<,o log _ m I I

' ACc, ENERGY LOSS levi I I _,,_

b! tri,li" <SATELLITES}....-I----s..,'{" _ +,,r" ,,",,7_d'_ossES.- .'./"' _ ,,- . ._:_'.,,, ',,,_;Z,,.,

L_ 1 t J .',,_B_-._ -':''_----s'_''--'-'- ..... " i990 910 930 950 0 o 20 _0 60 80 +0o

EA, AUGER ENERGY {eV) CHANNEL NUMBER

Figure 3. Cu L Auger spectrum Figure 4. Argon K photoelectronfollowinga vacancy spectrum at lowin the L2 subshell resolution.

ORNL.DWG 89.10103

Ar3S

1500 1978

il 14ili. el: iiiico;Bi Figure 5. Progressmade_= ..... 1 ' h.-7_,v in ESSR Studies:-' + _ *= Illustrationby way of

- -,.o,v +v_ the ArM photoelectron1

spectrum

500 _ _o :S _lS,li _s 'a lo '1, Xlt3 /'_ ' ' ' ' '' i

oh.SATELLITES

_

- 3d ] 1989

+,200 _. _ llO[ et ii4d

" i src -

800 F- i I I_aduiitor5d ' t by = 60 eV#m

_i}l

44 42 40 38 26 34 30 28 16 14-LECT_ON BINDINGENERGY (eV)

FROM _ "ZARLY DAYS' TO TEE PRESENT

•m 186

m,,i m

ORNL-DWG. 74.12171

E.4 , AUGER ELECTRON ENERGY (eV)

t ×104 2450 2500 2550 2600 2650

f i ' , , T I _' ' ' ....' i k....., , , 1 ' I , ,-Ty-_ _- , ....

ARGON K-AUGER L2Ls('D::)

L2L2(_So) [ L_L_('Pq.,i,.08" L bq

L_LI(ISo). L_La(IP,) L,L2z,(_P) _ I1/ "

l t ,fr;:o_ M f ":.'!li -

o . A "'_" '' ' " '

o -, 'z-__----_Z-_'i'j _ - i. ___.__..L.\ ._,,,._,._i, , J

-220 -2_00 -180 -160 -140 -120 -I00 -RO -60 -4.0 -20 0 ,20/',E, RELATIVE ENERGY (eV)

Figure 6. Argon K-LL Auger spectrum excited by electrons

}" iii. ,i ) 4

r

,s:_,mI *f

' 30-4 4o _ .- ........ ,1:q': ......800 I ,i_ L. - :

S.-t.,_E,JP

O0 _, i_.._a _ -;._)40.0

: *' , t '

- 0 "" _ ,.,I l II I - i

• 2540 2650 2_ 2870 '',/

AUGER ENERGY (eV)

-, ___; -_,,.3:"_" ,_

- i= "i- . • ....

= =,-,';TC¢,:.,_E._"3.' :,)

Figure 7. Ar K-L2 3L2 3 Auger lines excited by photons as a

function of energy187

Clearly, a higher resolution than availliblo iri ihis initial cxpcrin]ent and all e×tensi¢_ntc) other elements

and deeper core levels arc desirable i.o rigorously test existing theoretical lllt)dels. The high i'mst)luiit)n

K Auger spoctruni of Ai (Fig. f_) separates i'ail.ier well the llt)rlllal Ati_or lines arisirlg l'roill l,i single K

hole from the various satellite lirics arising l'rt)nl shiikcup or stillkcot'f iri the M arid L shells. 'l'hc

separation is, however, not complete, Iri ell'icr AI.igor spcclra there may be cvci'i greater overlap.

Tunirig the photons properly at'fords a lh'st at)prtmch to highlight certain groups as showii iri Fig. 8 l't_r

the N2 KI_.L spectrum' (a) the gross spectrum; (b) the spectator/actor spectrum associatcct with ls -->

2_ excitation (part of lt sometimes tel'erred tc_as resonance Augcr spectrum), and (c) the ist_latcd

normal spectrum, which is devoid o1"satellites. Ct_uld the Ai' K Auger spectrum bc partitionect similarly?

As the K absorption spectrum (Fig. 9) suggests, the i.iorrrial KLL spectrum could indeed be isolated by

selecting a photon encrgy i.irtlul.id 3215 eV. However, line shapes arid Atigcr energies would have to

be carefully interpreted because o1"the strorlg post-ct)llision iritcrliction of the slow photoclectrt)ri with

the Auger electron. As the nulnbcr of shells and elcctroris increases with Z, even the option of exciting

near thrcstloM becomes cluestit_,nal_le as illustrated in Fig. 10 ti)r ftle I_,_pl.iotoabsorption spcctrl, lm o1"

Kr. The final apt)roach t_ cleanly separate the ccmlponcllts eH' an Auger Sl)Cctrum remains thcri a

ct)incidence measurcmeilt between the ptmtoeicc/r(m and the Auger elcclrt)lls. A corresl)ondirlg

_lppr'.)ach applies to x-ray emissiorl spectra Its I will show tilter.

Orice merc I like t(+ return tc) Fig. I, The plate shows tw{) sets c)t' ccmstal.it-lcngth trncks, one o1'

whictl is _t" very shc+rt length. Auger atlributcd these two sots to Auger groups that are emittc t as a

result of _i VilCllilcycascade triggered by tlle initial inncrshcil ionizatiori. Such ii cascade is illustrated

in Fig, 11 for Xc and the idea i_t"_l stepwisc progression (_t'vacancies has served well t() explain the ion

cb,arge spectra t)bscrvcd, s l-Iowevcr, one might ask whether such a neat stcpwise progrcssi_n will always

occur in a multi-elcctr_ri atom c)r whether al'tor the sccc)lld or third step a giant, nlultichannel

"autc)it_nizatic_i.iCxl_losi<_n"c(_uld llt)t ;,icc_,'ltinlli)r the clbservcd charge distribution. The recording ot" the

Auger clc'.ctri_ns which in c_nc model should fall irito several distinct energy gl'otlps could give {111 IIIISV,'2".

Such experiments can be done iri the future, even in c{_incidence setups. Until now (rely one or tw()

sitidies, apart frt)nl the original _bservatiori (Fig. 1), have given art indicati{_n for two but not ti_r m_re

distinct groups tt_ bc assoc'iatcd with trarlsitioris t_) successive main shells.

/\notl'lcr cluestic)n which awaits defirlitivc experimerltal scrutiriy concerns the trends of certain

properties _,llt)l.ig_il.iist_clcc:trt_nic series. Such c:'xpcrimcnts involve i_ns _)1'iricrcasing charge lind, hence,

illorc and rn(,)re tel.iut}us taritets,_ and higher ;,li-ldhigher cnerg, ies,. I will give two exall.il)lcs. Many

elements, for example 13c and (.', disl)lay strong groundstatc ct)i'rclati_ns due to the adn.iixtt.ire of excited

stales. The Be Auger slitcllites <'give evidence of this ct_rrclation its seeri iii Fig. 12, arid it would be o1'

interest t_) explore how this type ot' correlation will change when the nuclear charge iricreases ahmg the

188

FIGURE 8

189

-

,.,EF_._ From Phys. Rev. A _._.,5123 (1986)

E"EE'I::_: L:itl,,p..4 5(5

5 t

--_,_- ;. 4 S e I

N _ _l,ez4_=,4 e

0 _ : C I.--I'_1P ;t 4 I_ ? 4D l lk_ | 4pnp"b d:j_D r _,(Z._ r_t}/

';=oo9s- _ . .../._.,,.._ _=,z,,,,Z ,.t,_ . ". 4'- Ca4{ ,I. "..

"'.. °

0 I0 ;_0 30 40 SO 600090. t I _ ; ' I

ENERGY(eV)

Figure 9. Photoabsorption spectrum of Argon justabove the K-edge

From J. Phys. (Paris) ._.?=,C4-88 (1971)li.VI' oppilents

?L_, tLm-Nra VLm-Nzo t o o

R_EgI(_ d'_b_;Egtj_ L'3.N

/_t du KRYPTO.._

!

, ' EeV0

Figure 10. Photoabsorptionspectrumof krypton just

above the L3-edge

190

ORNL-DWG. 64- 8705

A VACANCY CASCADE IN Xe

Figure 11=

Vacancy cascade in K-shell ionized xenon, showing the

most probable route in the case of a stenwi3e progression

191-

ORNL-- DWG 87-44254

3500 ' " '_....... ' " ''_ ' ' ' 'l

. r-'- 2s 2s Be

K-AUGER_J 2800 hu=130 eVuJZZ

d400lD

+ 7ua 2s 2pa_

PCno_Z t400- / 3pl _PI

0 _'_t'_O t,, +..... I

O 44 28 42 56 "tOCHANNEL NUMBER

Figure 12. KLL Auger spectrum of atomic beryllium

ORNL-DWG 88-17105

22 I _ I l i ... I I

• .

- Mn 3p

18 -

... 5p(4) 5p(3) Sp(2) sp(l) 7p

I I--.14 - -,-1

z

_" 10 -0O3_=Z

0 6 - "' .

, .,.

f ". °o ,+"'-

2 "r'-"."'-" ! .... P" "-'-T..... ! I",~,-'-"","l -

80 ';tO 60 50

BINDING ENERGY (eV)

Figure 13. Multiplet structure in atomic manganese arising

from photoionization in the 3p subshell

192

isoelectronic series. Would this effect be as pronounced for Ai"TM as for Be'? In the second example, 1°

the 3p photoelectron spectrum of Mn (Fig. 13) reveals strong intershell correlation of the type 3p z

3s3d and it would be instructive to compare the 3p spectra of Zn s+ and Kr 11. with the Mn spectrum.

Finally, emission experiments of this nature could also address wave function collapse when apprt_ching

d and f transition "_ 'scn!..s, however, in these latter cases the crucial answers are likely to ce,mc fmna

experiments done at lower photon energies.

Let mc now make an exmt_.rsioninto x-ray spectrometry. Nearly 20 years ago wc posed thc: question

whether so-called x-ray diagram lines, Ka, la, etc., are pure lines according to definition, n_lmcly Kcrl

= K _ L3, or whether these lines arc contaminated by parasitic satellites of the type KM _ L,M,

KN _ L3N, etc. This problem is akin to that discussed earlier for the Auger spectra, but it is

exacerbated tbr x rays because of thr _smaller shifts occurring between the lines of dil'fcrcnt origins. For

L x rays of a number of elements, the illusory nature of diagraln lines observed under normally

prevailing excitation conditions has been demonstrated in a few studies, but merc extensive v,,t_rk, iiided

by a strong tunable excitation source, is needed to be able to dctermine such basic quantities _s n_tural

line widths and absolute transition rates pertaining to a single hole state with an accur_lcy of better th¢ln

20%. Figure 14 presents a schematic illustration of the situation al hand as well as an experimental

method to disentangle the components. 1_ A conventional measurement of the Pb La_ x rliy yields a line

of 8.5 cV width (FWHM). If the La_ line is placcd into coincidence with the Ka_ (K - L3) line

following K ionization then a line of 6.5 eV width results. This is, indeed, the pure diagram line La_

(L 3 - Ms). The answer to the origin of the pseudo diagram line comcs from the coincidence with the

Ka, (K - Lz) line. The resulting line is offset from the true I..a_ line because it is a satellite L,N - NlX,/Jls

following the CK transition L2 - L3N, Under normal excitation modes, ionization takes piace in _lll L

subshells ultimately creating a complex "I.a_" line. The contamination of the I__ line by parasitic lines

has been investigated in detail for Zr. _z As seen from Fig. 15, the purity of the La line is generally less

than 75% and may drop below 50%. Both Ck)ster-Kronig transitions and shakcol'f processes contribute

to this effect.

Amor_g other applications of hard photons in atomic processcs (at thcsc energies princesses arc

essentially atomic regardless of the state of matter), I shall select a last one: that of the photoelectron

angular distribution and the effects of retardation. This is one of the more intriguing research, although_

:" its beginning goes back, once again, to the Wilson cloud chamber plates taken by P. Anger - and shown

in Fig. 1. In fact, the long tracks seen in Fig. 1 were the initial object of that study with the aim to

distinguish between the old and the new quantum theory by way of the angular distribution of the

photoelectrons. The work of the time relied on hard x rays in the range for which the APS is designed.

Due to momentum transfer, or retardation as we now prefer to say, the angular distribution is skewed

193

,0 - l

-,Oev E0 '0 -'0 [ 0 ,0 "_0 -qO ,_'g ,')ev

........, Ii 'I 2'_e STE D I I ?,_d STE;_'

_t STEP I I I

l II SAT. II Sir, III SIVlV"'*" t_''_''" t"*" _'°"', _. _. •

,_ACANICY SINGLE _OU_LE DOqJl_.E _ 1 IllPt..E DOUBLE InlPLE

/(Figure 14. The isolation of a pure diagram line in an arbitrary

case and in the case of the Pb LcKI x-ray line

hVPHOTON ENERGY(keV)L. 6 B 10 12 1_, 16

100T.... I '_ _ " _ ' : ' 1 . _ ' i

/ Zr L'%,2

/

..c_50

u ,..,/ TRiPL__ .-......-.---..---- "- "---

0 OS _ 15 2 25iNITIALVA_CY DISTRIBUTION L_,'(Lt',-LI}

Fi_lure 15. The composition of the Zr L_ x-ray linephoton-excited in the energy rangebetween the LI and K shells

194

Abb. 25. R.lchtun_eiluu4_ _ WK s in Argon. (NachAuosn;. Kurve berer.hnet nsr.h ¥xscn'tn.)

Figure 16. Skewing of the angular distributionof K photoelectrons in Argon

II. K. 'I'SI'_N(;, R. II. PRATT, SIMON Y U, ANID AKIVA lION

From Phys. Rev. A 1_Z7,1061 (1978)i2

_. U K " shell

: ooo5 ,_,J l'_,}_ 1332wev J- Io--O\ Pb K-shell

" .'_,_ -,-.,._,_ o ii m .__

O 30 60 O 30 60 O 30 60 90 120 150 180

8 Angle (deg)

(o) (b) (c)

Figure 17. The asymmetry of photoelectron angulardistributions in experiment and theoryfor three cases

.=i

195

forward as clearly evidenced in Figs. 16 and 17. Early calculations of the Sommerfeld school were in

good but not perfect accord with experiment for the K shell, and because of their approximate nature

in only fair accord for the L shell. 1_ More sophisticated calculations TMof the recent past gave improved

agreement with the body of experimental data existing at higher photon energies and, significantly, with

the few data available at low energies. This is shown in Figs. 18 and 19. An iselatcd study _sexists for

the M shell, that of Kr. In that work, the three subshells, s, p, and d, could bc distinguished and wcrc

shown to exhibit quite different angular distributions for the respective photoelectrons, but in satisfactory

agreement with theory. In particular, it was found that the 3d electron distribution was skewed tbrward

while that for the 3s electrons which have similar energies is almost symmetric, about 90°, indicating

that no higher multipoles beyond the dipole operator are active. Although there is a rudimentary

understanding of the higher multipole effects in angular distributions, we should remember that there

is only one experiment tbr shells higher than the K and L shells and very few cases in which the L

subshclls were distinguished. At the same time, _eccnt more elaborate calculations make some

unexpected predictions, especially near inncrshell thresholds. '6 This is an area where much work remains

to bc done over a wide range of energies, elements and subshells.

In the past, ali experiments were carried out with unpolarized radiation and this is reflected in the

plots of Figs: 15-19. With the polarized radiation emerging from a synchrotron radiation source,

detection of the higher multipoles arising from the e _u term requires a measurcnlent in the XZ

coordinates '7 as sketched in Fig. 20, where the complete expression for the angular distribution is given

ft_r the case that both the dipole and quadrupole operators contribute. TM Three cocfficicnt,; of the

t.orrcsponding Legendre polynomials enter the expression which is derived tk_ra polarization of 100%.

A more wieldy expression would apply to partial polarization of the photon beam. Fortunately, the

insertion devices which are an integral part of the new, third-generation synchrotron radiatk_n sources

yield a virtually complete polarization, of the photon beam, 99.6% as measured in one case, so that data

analysis is simplified and a high accuracy is obtained as demonstrated in Fig. 21 for the Bz dipole-

related/3 parameter in the case of He at low energy of photons emerging from an undulatc_r.

With this glimpse into the future and the promise expressed in several results (e.g., Fi3s. 5 and

21) that wcrc obtained on the way to the new advanced photon sources I like to conclude this

presentation, but not without cautioning that the increased power and energies of the advanced light

sources must be matched by improved users' apparatus to optimize the opportunities.

196

OerNLo0tll lt- 4_1t4@

I ' 1 on_.- owo It-iSH|

Ill K(WM a) Ne K(AI Ko) Nelll(M4l Ko) I 1

90_llV -- 61711V 38i41N -] i KrMIIMqKo) Kr MI_3(MqK o) KrM4s(MIIK(II)_ " ...... L ....... ',..___.__............. Z--_.___/

i-,Z Z I .......................

- . _.. - i(o )_i

ENERGYENERGY 120 r

lO0 :"- ._ _ I00

/ f

40 ! i - _ _.#_,_ -- _ z

_,oi/ / X X. ,,,_,o I 7f ,_-_,,+---d,'t-.......... -'_--'_<iii" _ /_'l '_Xl_ Kr M,(Mg Kel)_, //"__\, J ._,o.... :_ ...................,.,_,,..o

._4, ii. . _, | I!l_i,l|__ _NilIIWMo) "l"4u_, '_/_ ...... "--_4B,,0.237 "-i /.# SOL;D LINES; "\'_ I t

i _ SOLIOLINES: lt ,l_ #J'_ Jie,A,Oil'l'Aie sin:' # '_ I

0 30 60 90 IlO _50 iso 0 ] 0 60 9O *20 (._0 _80

_.,,_NGLE (deq) _},ANGLE (_leql

Figure 18. The effect of the eik'r Figure 19. As for Fig.18 but interm in the angular dis- the case of Kr M Shelltribution of photoelectronin Ne K Shell

x

• h- " >Figure 20.

(Note: the angle@ _- _ .._._ #/corresponds to 0 il_ rp#t t kin Fig. 16 andO

: in Figs. 17 to 19.)I

. + f"'#'_f'_

#

= 197

,,'/

15oo ,

f '._ 12oo03_C::03

900

Z

0.9960

_ 0.9955 ";' /'S/O_

.__ _°/

"+'O t /O_/ '.L'_-I 0.9950L.

0 •0.994.5 * i

2.008

2.004_ _, 'U I_,.., _,._1,. I L, _., .,1,, ' ,, __A.® ..ooo! _,___,I,_Nt/_AI_/_:_JW_J_AJ:'_,<__m., -IVIF '7" _,_"'i_'" ""'"

1.996 _If

L i ! • . .. I i I i ! --

58.65 59.15 59.65 60.15 60.65 61.15

Photon Energy (eV)

Figure 21_ The photon profile and polarization of radiationemerging from an undulator,(SRC, 1989), and the

, resulting high accuracy in the /9parameter as shownfor He ls ionization

198

z

References

Note: This list is far from exhaustive and is meant to simply serve as a guide.

1. P. Auger, Compt. Rend. (Paris) 17__27,169 (1923); Ann. Phys. (Paris) 6, 183 (1926).

2. M.O. Krause in Synchrotron Radiation Research, Plenum Publ. Corp. N.Y. (1930).

3. W. Mehlhorn in Atomic Inner-Shell Physics, Plenum Publ. Corp. N.Y. (1986).

4. Atomic Inner.Shell Processes, B. Crasemann, editor, Academic Press (1975);

S. L. Sorensen, et al., Phys. Rev. A3___99,6241 (1989).

5. H.W. Haak et al., Phys. Rev. Lett..41, i825 (1978).

6. M.O. Krause, J. Phys. Chem. Ref. Data 8, 307 and 329, (1979).

7. G.B. Armen et al., Phys. Rev. Lett. 54, 1142 (1985).

8. T.A. Carlson et al., Phys. Rev. 15__.!1,41 (1966); M. O. Krause and T. A. Carlson,

Phys. Rev. 15.__.88,18 (1967).

9. M.O. Krause and C. D. Caldwell, Phys. Rev. Lett. 5..99,2736 (1987).

10. J. Jimenez-Mier et al., Phys. Rev. A4___Q,3712 (1989).

11. J.P. Briand et al., in Proceedings of Int. Conf. on Physics of X-Ray Spectra. NBS (1976), unpubl.

12. M.O. Krause et al., Phys. Rev. A__.66,871 (1972); F. Wuilleumier in Proc. Int. Conf. on X-Ray

Spectra, Univ. Miinchen (1973), unpubl.

13. W. Bothe in Handbuch der Physik vol. 23.2, Springer (1933).

14. H.K. Tseng et al., A1.__._77,1061 (1978).

15. M.O. Krause, Phys. Rev. 17._27,151 (1969).

i6. Y.S. Kim et al., Phys. Rev. A22, 567 (1980); A. Bcchler and R. H. Pratt, Phys. Rev.

A3____99,1774 (1989).

17. J.H. Scofield, Physica Scripta (1990), in press.

18. J.W. Cooper (Private communication).

Acknowledgemeat

Research sponsored by the Division of Chemical Sciences, Office of Basic Energy Sciences, U.S.

Department of Energy under contract DE-AC05-840R21400 with the Martin Marietta Energy Systems,

Inc.

199

Beam-Line Considerations for Experiments with Highly-Charged Ion_*

Brant M. JohnsontDepartment of Applied Science

Brookhaven National Laboratory, Upton, NY 11973

The APS offers exciting possibilities for a bright future in x-ray research. For example,measurements on the inner-shell photoionization of ions will be feasible using stored ionsin ion traps or ion beams from an electron-cyclotron-resonance ion source, or perhapseven a heavy-ion storage ring. Such experiments with ionic targets are the focus for thediscussion given here on the optimization of photon flux on a generic beamline attheAPS. The performance of beam lines X26C, X26A, and X17 on the x-ray ring of theNational Synchrotron Light Source will be discussed as specific examples of beam-linedesign considerations.

iwith K.W. Jones, M. Meron, M.L. Rivers and P. Spanne (Department of Applied Sci-ence, Brookhaven National Laboratory) W.C. Thomlinson, D. Chapman and J. Hastings(National Synchrotron Light Source Department, Brookhaven National Laboratory).

"Research supported by the Chemical Sciences Division, Office of Basic Energy Sciences,US Department of Energy, under Contract No. DE-AC02-76CH00016.

In Sep',ember of 1980 the "Workshop on Atomic Physics at the NSLS" was held ai,Brookhaven National Labcratory. Considerable interest and excitement was expressed for

the potential impact on atomic, molecular _,nd optical (AMO) physics research promisedbF' the new National Synchrot.ron Light Source t NSLS), which was then under construc-tion. Many of the conclusions and areas o," interest evidenced in the proceedings of thatworkshop are stiii true today. For examp',e, (1} the AMO physics community is muchmore intel, est.ed in soft-x and VUV photons, i.han in hard x rays; (2) there have been very*"ewmeasurements on the photoionization ef iGns, particularly for inner-shells', and (3)

; i.he next generation fa.cility will undoubl.edly enhance experimental capabilities in currentresearch programs and foster the development of new research endeavors.

_. ExperimentM progress in the decade since the NSLS workshop is well documented in" other contributions to this APS worksliop. Some of the specific experiments performed

on beam lines X26C at, the NSLS are discussed or mentioned in the contributions bF,)>ave Church, Bernd Crasemann, and Jon Levin. Some of this work was performed inoollaboration with ,esearchers from Texas A&M, the Universi,v of Tennessee and Oak

Ridge ?lat, ional Labor_'..tory, Argots.no NationM Laboratory, and St,. Etienne, FRANCE.AdditiorM studies of synchrotron-radiation (SR)induced fluorescence spectroscopy and

the direct inner-shell photoionization of ions from a conventional ion source are carriedout. by the local BNL group, but the)" will not be discussed here.

The rel_,tively small number oi practitioners in AMO physics wilh hard x rays is botha blessing and a curs¢. The good news is that the field is wide open with more excitingideas and possibilities than current researcbers can possibly investigate. The down side isjust that - ii. has proved difficult to interest o_her experimenters (and funding agencies) to

-I turn their attention toward hard x-ray research in AMO physics. Perhaps this workshop: wi!l serve as a catalyst to stimulate interest in the illuminating possibilities thai the APS,

the ESRF, anci the SPring-8 will offer.

o Unqu___tionably, the new tMrd generation hard x-ray photon sc.urces will provide sub-stantially mt_re x rays than second generation machines (such as the NSLS x-ray ring).However, experimental beam lines must be carcfully designed to realize the full potentialof a third generation photon source. Figs. 1-2 give an over-_iew of generic beam linecor, siderations.

The specific characteristics of beam lines X26C and X26A, with particular emphasison the performance of a l:l cylindrical focussing mirror, are discussed in Figs. 3-9. Therelativo perfocmance ,:ff APS undulator A and bending magnet beamlines ai. the NSLSand APS are co:npared iri 'Fig. l0 and dis,:ussed in Fig. 11 through the example ofmeasurements of the radiation produced by the NSLS superconducting wiggler on pori2X17.

_t

_l'he PHOBIS concept for producing highly-charged ions through successive photoion-izalion of trapped ions is reviewed in Figs. 12-13. Finally, an overview of a proposed

. !:eavy-ion storage riv.g for use at a hard x-ray light, source is given in Figs. 14-24.2

201

BIBLIOGRAPHY

ATOMICPHYSICS RESEARCH ON BEAMLINE X26C AT THE NSLS

B. M. Johnson, M. Meron, A. Agagu, and.K.W. Jones,Nucl. Instrum. and Meth. B24/25 (1987) 391.

PROPOSAL FOR A HEAVY-ION STORAGE RING AT THE NSLS

K.W.Jones,B.M.Johnson,M. Meron,Y.Y.Lee,P.Thieberger,and W.C.Thomlinson,Nucl.Instrum.and Meth.B24/25,(1987)381.

K.W.,/ones,B.M.Johnson,M. Meron,B.Crasemann,Y.Hahn, V.O.Kostroun,S.T.Manson, and S.M.Younger-,Comments At.Mol.Phys.20 (1987)I.

FeasibilityStudy (1988);DOE ConceptualDesignReport 0989).

BASIC REFRENCES ON RESEARCH WITH SYNCHROTRON RADIATION

Introduction to ,Synchrotron Radiation by Giorgio Margaritondo,Oxford University Press, New York (1988).

Ha,,dbook on Synchrotron Radiation, Ed. Ernst-Eckhard Koch,North Holland Publishing Company, Amsterdam (1983).

202

GENERALCONFIGURATIONFORSR EXPERIMENTSafter R.L.Johnson (pp. 173-260)in

Handbook on SynchrotronRadiation,Vol. lA

N(hv) Source Photon FluxPHOTON _ox HorizontalSource EmittanceSOURCE

_oy VerticalSource Emittance

TB BeamlineTransmissionCoefficientI _, HorizontalBeamlineEmittance

PHOTONBEAMUNE

t _ VerticalBeamlineEmittance

TM Mon. TransmissionCoeff"K_ientMONO- O_, Mon. HorizontalAcceptance, CHROMATOR

c_y Mon. Vertical Acceptance

EXPERI-MENT _ut(hll) Photon Flux for Experiment

Nout(/_)--- N(X) TBTa (Cxhl×)(C vhly)

Fig. 1 illustra.tes the relevant, parameters that determine the photon flux Nout(_) ava.ilable for= an experiment. In the equation given at the bottom of the figure; 8 x is the horizontal

divergence angle of emitted radiation from the bending magnet or insertion device ofinterest.

S

203

Nout(X)= N(X)0×TBTM

TO MAXIMIZE PHOTONFLUX FORASYNCHROTRONRADIATIONEXPERIMENT:

1. Design Light Source forMAXIMUM PHOTONFLUXand MINIMUM EMITTANCES(Horizontaland Vertical).

-

2. Design both beamlineandmonochromator to acceptLARGESTPOSSIBLESOLID ANGLES.

3. MATCH ACCEPTANCESof mono-chromator and beamline tothe emittance of the source.

4. MAXIMIZE TRANSMISSIONofbeamline and monochromator.

Fig. 2 describes the design crii.eria for optimum photon flux on a generic synchrotron radi-ation (SR) beam line. As the equation from Fig. 1 impt!es, the source photon flux,Ox, transmission of beam line and monochromator, and monochromator acceptancesolid angles should be maximized, while the emittcnce of the source and beam lineare minimized. A fuller desc,iption of this and other considerations are given in the

general references listed in the bibliography.

204

' I!I_

_ Fig, 3 is a schema.t,ic repret;_ntat, ion of the si,o:'age rings and bealn lines of t,he NSLS x-rayand VUV bea.m lines. The loca.t, ion of bear:': port, X26 is indica.t, ed.

!

205

_.w,-.._ Beam Lines X-26A and X-26C at the NSLS

k- ,2_ k-- 11r. _- 1orek-9m k- 8m F 7m F sm _ 5m F-4m k- amF" 21m I_-20m I(-- 19m le- 18m I(-- 17m _- 16m I_- 15m I(-- 14m I(-- 13m I_- 12m

g ........................ -

Fig. 4 gives the layouts of beam lines X26C .nd X26A on the X26 t_eam port of the NSLS):-ray ring ai the NSLS, Note thai. r'either beamline presently has a, monochromator,but. that each has an x-ray focussing mirror, On X26(I a 1:1 cylindrical mirror is

located at, about 10 m from the photon source point t,o produce an image in theexperimental hut, cb at about, 20 m, On X26A an 8:1 ellipsoidal ulirror is posii, ionedai 8 m to produce a focal spot at about, 9 m.

206

X-RAY FOCUSSING MIRRORS

1"1 CYLINDRICAL

- 8:1 ELLIPSOtDAL

1"1

8:1

Fig. 5 shows the two focussing mirrors. The l'l mirror is made of Zerodur; is coated withplatinum; is 60 cm long; and accel_'_s 4 mr of horizontal radiation. The 8'1 mirroris :.;ade of elect.roless nic!:e!: is coated with platinum; is 20 cm long; and accepts 2

' ,, 1/

mr of horizontal radiation. __,'_h m,rrors are u',,.,u at an angle of incidence of about4 mr giving a high-energy cut.off at about 1,5keV. For a bending magnet or wiggler

,, at. the APS it might be desirable to try t,o focus the harder radiation above 15 keV.The cut.off can be moved to about 40 keV by lowering the ,_ngle or incidence to 2 mr.The APS experiments will more typically be located at 40 m from the ring with a

- mirror at. 20 m. The hand-drawn sketch indicates schematically (in a two dimensional_- representat.ion) how the mirrors operate. Imagine th, ellipse rotated a few degrees

each way about its long axis to produce sections of cylindrical and ellipsoidal surfaces.2 Reducing the incidence angle and increasing the distance between the foci amounts to- stretching t,he whole ellipsoid and shrinking its minor radius. A 1'1 ,lirror of about

the 'ame length at 20 m from the ring with a 2 mr angle of incidence would accept'3 ionly about , mr of horizontal radiation, instead of the 4 mr accepted on X.,6(,.

207

/ i ¸............. .....

NSLS X-26C 1:1Focussing Mirror ) , qllj

Fig, (3shows an anamorphic drawing (transverse dimension greatly expanded) of the X26(',

beam line. The horizontal focussing action of the 1:1 mirror is indicat.ed in the planview (upper) and the vertical deflection is illustrated in the elevation view (lower).

Figs. 7-9 illustrate the measured performance of the 1'1 cylindrical x-ray mirror on X26C. ASi(Li) x-ray detector was positioned at a forward scattering angle of 45° to measurephotons scattered through air after passage through a 20 x 20 #m pinhole,

208

Scatter fromAir

10"...---_-T., . , _.,., , , ,...., • ,-, , . ,-_4

: Af I(_ , -..._,%Focu s.sed, t 11T_0t

lo'

O

-=_glo'

t3 101 , 1 , I ' ' , ] , , , _ _

0 2 4 6 8 10 12 14 16 18 20

X-ray Energy (keV)b

Ratio of focussed to unfocussed beam

........... tt00.0

Ka

80.0

Pt L edges

40.0

20.0

0.0

= 0 2 4 6 8 10 12 14 16 18 20

X-ray Energy (keV)

Fig. 7 (upper) shows the measured x-ray energy spectra for both unfocussed and focussedradiation with the pinhole positioned for maximum intensity. Fig. 7 (lower) displaysthe ratio of these two spectra. Note that an enhancement of two-orders of magnitudeis realized over a wide range of photon energies and for the characteristic Ar K x-rayproduction produced from argon in the air. The dip ai. about 5 keV is artificial. Dueto the low x-ray scattering cross sections near this photon energy there are 'very fewcount,s in the scattered-radiation spectra.

209

Fig. 8 is a two:dimensional line plot of the photon flux dist.ribution produced at the focalpoint, with the 1'1 mirror. Note that the focal spot. is nearly round. The unfocussedhorizontal image would have been about 8 cm wide. The full-width-_t-half-nlaximunlor 2ct of the focussed image was about 0.7 mm. Although the mirror specificationcalled for no vertical focussing the verticM beam profile had a 2ct of 0.6 mm, while theunfocussed, was 1.8 mm. This factor of three reduction in vertical height is believedto result from slight, concave curvature down the long axis of the mirror,

210

Focussed beam. profile (horizontal)10.0 ---.- _ .... I - , i .... ,,I I -- I I I

8,0

'_ 6.0

,_",,W

,I,.0Z8h

2,0

0.0 , I I j I , I pkxx_"_::::_

5t 50.a 50.8 50.4 50.2 _0 _.8 49.6 ,9.4 _.2

Horizontal position (mm)

_o Focussed beam profile (vertical.)tO.O - _ l r i i_" I I' I I

V

c_ 8.0 -¢,)

,,,,w,,p

6.0

4,0--

2.0=

_

0.0 I "_._ L_..f-__

82 8.t,B 8t.6 Bf,4 8t,e at 80,8 80,6 BO,480.2 80

Vertical position (mm)

- Fig. 9 shows the horizontal and vertical beam profiles at maximum intensity, The vertical

" profile is asymmetric only because it was clipped on one side by by an aperture in thebe,_m line.

211

Fig, 10 shows the calculated photon-energy spectra for the un(lulat.or A of the APS comparedto those for a typical bending magnet beam line (X26) and a super-conducting wigglerat maximum field strength of ,5 Tesla (XI7), The X17 spectrum (at 4.9 Tesla) is alsotypical of a generic bending magnet at the APS, although, flux at the APS may beso,newhat higher due to the lower source emittance. At, a field strength of 1,1 Tesla,X17 produces essentially the same spect, rum as an NSLS bending magnet port (e,g,x26). Clearly, an undulator provides much higher photon flux at soft. x-ray energiesthan bending magnets or even super-conducting wiggters at the NSLS.

21.2

Scatteredspectra from Si02glassat X-1710' ......- ' I ' I ' 1 ' i • i '

.

" ____,,_ iI PbK fluorescence103

lo'

_ 0 20 40 60 80 100 120

, X-ray Energy(keV)

Ratioof high/low field flux on superconductingwiggler; 10' - , r--,--r---,-----r----__=

J "

_=lO'

_ lO'

o

- lo'"8.oa: 10'

10o , .,,,'1" L J .., 1 , . I , 1 _ J . _ ; ,

0 10 20 30 40 50 60 70 80

X-ray Energy(keV)

. Fig. II is similar to Fig. 7, but here a measurement is made of unfocussed x-ray scattering- front o, glass target on XI7 at 1.t and 4.9 Tesla with only 2 ma of stored electron

beam. The upper spectrum shows the t,wo radiation patterns and the lower comparesthe measured and predicted ratios. The energy dependence of the ratios agree well.The discrepancy in magnitude is attributed to either the loss of some beam when themagnet was ramped down from 4.9 to 1.1 Tesla or a normalization problem with thebeam monitors at such low stored beam currents. Note that this direct comparison of

- the two radiation patterns under otherwise similar conditions indicates that an APS_: bending m_gnet beam line is clearly superior to a comparable NSLS line only at hard- x-ray energies above a few keV.

213

flit

,, . ,_

10"pE"T"TTTTI-III. I ,,,,,m , ,'_ 10mm w

[,,

10-_ -, 10•

, ,,,WIGGLER - O

10._ ' 10_.o #,,

-O ,. % -I,,,,.,."% ti :

CD -20 _ % 13 E_. 10 , 10 •% O0

E X-260 Z

b 10.2,_ BENDING (_t 10_MAGNET ' _ "=

Z10_ 10"

Be WINDOW

ABSORPTION

10-23 10_° _10' 102 103 104 105

E(eV)

Fig. 12 shows the photon flux distributions for a t,ypicaI NSLS bending,m_gnet (X26(Land wiggler (X2,Sj, and the filtering effect of a Be window which absorbs low-ener,

l)hotons. Note lhat the _qux is plotted for photons in _ 1 eV energy bandwidl-rather than the more customary 0,1% wavelength bandwidt, h, Also indicated are t,;_

photoabsorption cross sections for the M-, L-, and K-shells of argon, Note that bro_t/

b,_nd radiation from either the bending magnet or wiggler span the entire rangebincling energies for. ali elect.rons in argon. £he same would be true at the APS 1_even the heaviesi, atoms,

214

PHOBIS:PHOtonBeamIon Sourcei e

' electrL_ I III II I

'; ions extracted_I |Q

,' from trap 'f'II IQ

e ;.A

_J_ t1_ "_, will '

M III1_ _ II "'I1.. ".. Ib

O.IROMATOR "",:,',::

, 7 "'_'--.. ..:'"_ / I / -°*,. "°_. _.4,',*

! SPECTR. / _ "'...,[':;."_ MIRROR

Adapted from K. W. Jones, B. M. Johnson, and M. MeronPhys. Lett. 97A, 377 (1983).

Fig. 13 illustrates the PHOBIS concept,, which was proposed many years ago, The basicidea is to use an ion trap t.o hold ions in the path of broad-band synchrotron radi-at,ion to successively photoionize ions to higher and higher charge states. The first,experimental demonstration of successive inner-shell photoionizat, ion in a Penning iontrap was recently achieved in a collaborative effort on NSLS beam line X26C. See the

contribution t,o these proceedings by David A. Church.

= 215_

NAPFNationalAtomic Physics Facilty

NAPF

A CooledHeavy IonStorageRing

._.oposedto be builtat the

T National Synchrotron Ught Source NA SD LL to be injected with ions from the S

TandemAccel-DecelLaboratory

at BrookhavenNationalLa

CHISR

Fig. 14 inl.roduces the basic elements of NAPF. the proposed National Atomic PhysicsFacility. Such a facility would be ideal for studies of the inner-shell photoionization, ofions with hard x. ravs, as well as a host of other ion-photon, ion-electron, and ion-atominvestigations.

216

ATOMIC PHYSICS FOR THE 90's AND BEYOND

FUb DAMENTAL INTERACTIONS

, THREE-BODY CO_ COULOMB PROBLEM

. QED EFFECTS AT HIGH-Z

• STRONGLY PERTURBING INTERACTIONS

• MANY.BODY [NTERACIqONS/CO R.REI-ATION

. ATOMS IN VERY HIGH FIEI/9S

• TIME REVERSAL & PARITY NON-CONSERVATION IN ATOMS

• FUNDAMENTAL CONSTANTS

POORLY UNDERSTOOD PROCESSES

• COLLISIONS OF IONIZED SYSTEMS

• CHARGF T_NSFER,,

• ELECTRON COLLISIONS WITH HIGHLY-CHARGED IONS

• PHC_FON INTERACTIONS WFITI IONS

• ELECTRON-ION RECOMBINATION

• LASER-ASSISTED PROCESSES: LASER + SYNC'I_OTRON, ETC

• DECAY OF MULTIPLY-EXCITED IONS

• _XF_TATIONS OF QUANTUM CHAOS

, IMPORTANT APPLICAT!ONS

• FUSION PLASMAS

• ASTROPH'YSICAI. PHENOMENA

• DEFENSE

• F__RTH AND PLANETARY ATMOSPH]ERES

Fig. 15 summarizes the scientific justification for NAPF. See also the the document, s listedin the bibliography and the contribution to these proceedings by Steve Manson.

217

Fig. 16 indicates the proposed local, ion of-a heavy-ion transfer line from the BNL t,andem

facility to t,he NSLS. The existing transfer line tc) the BNL Alternating Oradient,Synchrol, ron AGS is also shown.

218

CHISR:COOLEDHEAVYIONSTORAGERING

Fig. 17 gives a schematic diagiam of the photon beam from the NSLS x-ray ring interactingwith stored heavy ions.

219

=

" ,, I, ..... III 'I!

BeamLineX-13at the NSLS

COOLED MAIN SIDE APERTURES FRONTHEAVY ION BEAM PORT AND I_O

STORAGERING ,EI'ATIO#; STATION SHUTTERS ------)

'3 Hutch B2 Hutch B1Hutch C Hutch Aux, Hutch Tunnel

% "., .

, ;.,

..... :.. _ • ._- % ..... .--.._ _ '

/ I v..,

/ _-_oto_.Shu,,_'--TailPieceExtension,

Fig. 18 shows some det_dls of the design of a specific superconducting-wiggler beam linel)rOl.,_sed for port X13 at. the NSLS, Note the provision for independent experimenl, t,on the photon beam line during time periods when the heavy-ion storage ring wouldnot be available for SR experiments.

220

=

Fig, 19 illustr,'xtes the wide range of mea,surenlents that would be possible in studying ion-photon, ion-electron, and ion-ion interactions ai, NAPF,

3

"2_

221

PHOTON-ION LUMINOSITY

PHOTON BEAM INTERACI'ING WITH STORED HEAVY IONS:

Imrad ._.._ _

PHOTONS " "

o.o2mrada = 1.2cm b = 6cre "'"-_-_

•, O, 60m A = axb [IONS

NHIN PL - fA enc

Np rene = 1 x 1014 photons/sec-mrad

BANDWIDTH OF 0.1%

b

DEBUNCHED: NI.II = NTOT2,R

b

BUNCHED, 1 > b: NI.II = NTO T Ml

BUNCHED, 1 < b: NHI = NUMBER OF IONS IN ONE BUNCH

Fig, 20 describes the figure of merit for a crossed photon - heavy ion beam experiment-namely, t,he photon - ion luminosity, Tile parameter fenc is the frequency of encounter,which is typically 1 M Hz or 108 passes per second of the stored heavy ions,

222

ConsiderK-shellPhotoionizationof Cu _+

Assume photon energy resolution&E/E of 0.1%(better than 8 eV)and photon flux of 10_ Hz.

m,i w Ni ua ow ml NI lm un on al | m lul iI | | ali qln um alu Q_nnlu | | | | | w m

SIGNAL (K-shellphotoionizationevents)

Cross Section 3.0 x 10-20cm2(near K-edge)

Luminosity 4.3 x 1020cm"2s"_(Ion-photon interactions)

SIGNALRate 13Hz, ,n _ _ ,u ,,m,_

BACKGrqOUND:(Interactionswith ambient gas, 10"_ Torr)

Cross Section 2 x 10.= cm2, ,

(K-shellvacancy production)

Luminosity 2 x 1025cm"2s"_(2.9 MeV/u beam energy)

Fig. 21 begins _. cMcul_t, ion of expected signal to noise ratios for a_ specific photoionization

measurement in CHISR at NAPF (to be continued in the next fi,_ure),

223

K'shell Photoionizationof Cu _+ (Continued)

Synchrotron Radiationis PULSED.NSLSx-ray ring normally operated with 25 bunches.w ,,_.,,a,,,d,,w,.,.a ,..ii,_,w _,m,_ ..,,,.J,m _,m,w mm _. In _ _ w _. w _ w _ w _ _ w m w | m m | m w | I m m m m m | n n I m w n w m I

Bunch Width (4(7) 0.6- 1ns

RevolutionFrequency 567.7ns

Duty Factor 01026 - 0.044

TypicalDuty Factor 0.03ali

SIGNAL/BACKGROUNDratio 13/(4000 x 0,03)= 11%m m0m Imnlm m m m _ m mm m m Ima, mumm, ml0mm m m mm _mm _m_m_ _mu_m_ n_ n _ m_mmum mm

Similarcalculationsfor outer-shell ionizationof Cu ionsyield SIGNAL/BACKGROUNDratios of 3 to 9%.

CONCLUSIONCHISRexperimentson thephotoionizationofions(bothinner-andouter-shell)arefeasible,

Fig. 22 the continuation of the calculation begun in the preceding figure. Note thai. theconclusion would be ew, n more valid for a similar proposal at the APS, Instead ofa long and costly transfer line from ATLAS, an ECR ion source and linac near the

('HISR could be used for injection.

224

loe '1 1 I I

106" C 8 - _ _._/Au

104 CH6,_R -

2 1°s ......... -- -aL

102- . -

t01 -ECR

N

_0e - Aw -!

'r i•i0" I , i ,, , ,,0 10 20 80 40 50

£)

Fig, 23 compares effective beam currents for a Cooled Iteavy-Ion Storage Ring versus anElecl, ron-Cyclot, ron Resonance Ion Source. ,The overall magnitudes are very dependent

- on specific assumptions about the performance of each type of ion source, but the trendversus increasing charge state is generic. ECR sources are compet.i(,ive at. low chargest,at,es and for light, to medium Z element, s, but CHISR clearly wins as the charge staleand mass of the ion is increased.

225

I a

110keV10-21 I I I I

0 20 40 60 80ATOMICNUMBERZ

Fig. 2,1 gives plots of I._hol.oionization cross sections versus Z for K-, L-, and M-shells of alielements. Note that t,he elements ancl shells covered by different ranges of soft andhard x rays are indicated with dashed lines. While inner-shell studies over a widerange of low to medium Z ions can be performed with soft x rays, such experimentson heavier atoms require the much harder x rays available in abundance at the APSor on a superconducting wiggler at. the NSLS.

226

Spectral Characteristics of Insertion Device Sources

at the Ad:,_._:_:_ Photon Source

P. James ViccaroAdvanced Photon Source

Argonne National Laboratory9700 S. Cass Avenue

Argonne, Illinois 60439

INTRODUCTION

The 7-GEV Advanced Photon Source (APS) synchrotron facility atArgonne National Laboratory will be a powerful source of hard x-rays with

energies above 1 keV. In addition to the availability of bending magnetradiation, the storage ring will have 35 straight sections for insertion device(ID) x-ray sources. The unique spectral properties and flexibility of thesedevices open new possibilities for scientific research in essentially every

area of science and technology. Existing and new techniques utilizing thefull potential of these sources, such as the enhanced coherence, uniquepolarization properties, and high spectral brilliance, will permitexperiments not possible with existing sources.

In the following presentation, the spectral properties of ID sources arebriefly reviewed. A summary of the specific properties of sources plannedfor the APS storage ring is then presented. Recent results for APS

prototype ID sources are discussed, and finally some special x-ray sourcesunder consideration for the APS facility are described.

GENERAL PROPERTIES OF ID SOURCES

Both undulator and wiggler IDs at the APS will be composed of magnetarrays in a planer geometry which set up a spatially oscillating magneticfield along the length of the device [1]. These arrays can either be made upof permanent magnets, with or without high-permeability magnetic poles,or electromagnets. Whatever the structure, the spectral properties of the

devices is related to the peak magnetic field, B0 generated. In particular,

the field results in an oscillating trajectory of the particle beam through thedevice. The amplitude and maximum slope angle depend linearly on both

the field, B0, and the period of the device through the deflection parameter,=

K, defined by:

227

K = 0.933k0B 0 ,

where k0 is the ID magnetic period in cm, and B0 is in tesla. For a K lessthan approximately 10, the maximum Slope angle is given by,

e =K/7,where 7 = 1957 E r is the relativistic factor, and E r is the ring energy in GeV.This is to be compared with the natural opening angle of synchrotronradiation,

which is approximately 73 krad for the 7-GEV APS storage ring.

The spectral properties of a given device will depend on the relative

values of the maximum slope angle, 0, and the opening angle, _t. In the

undulator regime, where K ~ 1, the radiation from each part of thetrajectory is within the radiation opening angle, and interference effectscan occur. This interference causes spatial and frequency bunching which

gives rise to the typical undulator spectrum consisting of narrow bands ofradiation called harmonics. The energy at which these harmonics occur

depends on the ring energy and the peak magnetic field in the device. For asingle radiating particle, the radiative source size and divergence dependon the wavelength of the x-ray and the length of the undulator. Typically,the radiative divergence at the harmonic energy is a fraction of the natural

radiation opening angle, _t, and the photon flux at thisenergy is enhanced.

In the wiggler, where K > 5, the output from the device is a sum ofJ

intensities from each magnetic pole and the spectral output i:; similar to a

bending magnet, but contained within a horizontal angular range of _+K/7.

The spectral output on-axis is approximately N times the output from anequivalent bending magnet source, where N is the number of' magnetic

. poles.

The spatial and angular distribution of the particle beam will affect theundulator spectrum most severely. Since the particles in the beam areindependent, the effective source angular distribution and size .are aconvolution of the radiative and pa-ticle beam distribution parameters,. The

particle beam distributions are approximately Gaussian as is the case forthe central radiation cone at the principal harmonics. For the low-

emittance APS storage ring, the particle beam vertical divergence is on the

order of the Gaussian width (9 urad) of the first harmonic central cone. Inthe horizontal direction, it is a factor of approximately two larger. As a firstapproximation, information concerning the number of photons in a given

bandwidth contained within a given angular aperture can be estimated for

228

the principal harmonics using the convoluted effective source spatial and

angular properties.

The on-axis brilliance BL 0 (sometimes referred to as brightness) isdefined as:

BL 0 = number ofphotons/(0.1%BW mm2mrad 2)

and is equivalent to the total flux at a given photon energy in a fixed

bandwidth (BW) divided by the effective radiative source size and effective

_Jurce divergence in the vertical and hoI_zontal directions.

The on-axis brilliance at the principal harmonics of an undulator

contains information concerning the approximate angular distribution of

the source. In fact, the peak angular flux density of the central radiation

cone is given approximately by the product of BL 0 and the effective source

area. As mentioned, the angular width is the convoluted width of the

particle beam divergence and radiative width.

APS RADIATION SOURCES

Several IDs have been identified as standard x-ray sources for the APS.

These include two planar undulator and two planar wiggler sources.Undulator A, which has the Nd.-Fe-B and vanadium permendur hybrid

geometry, is capable of spanning the photon energy interval fromapprox:imately 5 to 30 keV using first-harmonic radiation. Undulator B,

which also has the hybrid structure, is tunable for approximately 13 to 20

keV. The wigglers A, with the hybrid structure, and B, which has

magnetic structure based on electromagnets, have critical energies of 32.6

and 9.8 keV, respectively. These critical energies are above and below that

for the bending magnet radiation of 19 keV.

In addition, several other devices are described. One of these is an

undulator-wiggler source. This ID for K-values near 1 behaves like an

undulator with a first harmonic in the range of 1 to 2 keV. At closed gap,

and with K - 9, the device is a wiggler with critical energy near 30 keV.

Undulator C is an x-ray source with first harmonic spanning the interval

of 0.5 to 1.5 keV. Both devices are very effective sources spanning the

interval between soft and hard x-ray sources.

The flux through a pin-hole with an angular opening equal to theangular width of the central radiation cone for the first harmonic of

Undulator A is approximately 1013 photons/sec in 0.1% bandwidth at the

229

energy of 8 keV. This value is typical for most undulator sources at the

APS. The total flux within the central radiation cone is approximately 1014photons/sec per 0.01% bandwidth at 8 keV.

APS UNDULATOR PROTOTYPE RESULTS

As part of the R&D effort, the APS has developed two prototype undulator

sources in order to evaluate construction techniques, critical construction

tolerances, and performance. The first of these is a prototype of undulator

A with a period of 3.3cm and a length of approximately 2 m. It was the

first short period undulator to be used as a synchrotron x-ray source. Thedevice was installed on the CESR/Cornell storage ring for a one month

dedicated rxm[2]. The storage ring was modified to have approximately the

same vertical emittance as the APS. The performance of the device was

excellent and satisfied all the requirements for an undulator of this type

installed on the APS. As part of the performance evaluation of the device,

the effect of introducing a taper in the undulator gap was tested. In this

mode, the first harmonic bandwidth increased by a factor of two. At the

same time, the spatial distribution remained essentially unchanged. Thisresult can be explained by the fact that the band width is determined

essentially by the difference in entrance and exit peak fields caused by thetaper in the gap. The spatial distribution at the harmonic, on the other

hand, is determined by the energy of the emitted photon.

A second prototype is the undualtor for the U-5 straight section at the

VUV storage ring at the National Synchrotron Light Source (NSLS). The

device will be used by a multi-institutional mate_als research group in adiverse program. The undulator, which was delivered to the NSLS in

March 1990, will be tested and its performance evaluated in early summer

of 1990. The device has a period of 7.5 cm and a length of 2.3 rh. It has the

lowest random field error of any built to date. Some of the essential designparameters can be obtained from [3].

SPECIAL PURPOSE IDs

Part of the R&D effort in this area will be placed on the development of

techniques which utilize x-rays with a variable degree of elliptical

polarization of ID sources in the region of 2 to 100 keV. In the low-energy

part of this spectral region, techniques used for the investigation of elastic

magnetic scattering and polarization processes will be prominent. In _e

high-energy portion of the spectrum, magnetic Comj)ton scattering will beE

230

II_

important.

At present, there is a significant amount of activity concerning the

development of ID sources capable of producing circularly or elliptically

polarized x-rays. These include:

° Asymmetric Wiggler [4]

• Elliptical Motion Multipole Wiggler[5]• Helical Motion Crossed Undulator[6]

• Planar Helical Field Undulator [7,8]

• Crossed Planar Undulators[9]

Of the possible ID configurations, two have been chosen as candidate

sources of variable polarized x-rays on the APS. The first is the crossed

planar undulator first proposed by K. J. Kim [9] which is an efficient source

on the APS for producing circularly polarized x-rays from 1 to 5 keV.Third harmonic radiation would extend tile range up to 8 or 10 keV. The

major advantage of this source is its time modulation capability since the

degree of polarization depends on an electromagnetic phase shifter. Theconceptual design consists of two hybrid sections with Nd-Fe-B magnets

and vanadium permendur poles. The sections are in tandem with an

electromagnetic phase shifter between them. The total length of the device

is approximately 2.5-m.

The second device is a version of the elliptical motion multipole wiggler

which has been recently been tested at the Photon Factory-KEK[5]. The

device proposed for the APS has a period of approximately 20 cm and is 1 m

in length. The critical energy will be approximately 30 keV and the device

will span the range from above 8 keV to approximately 100 keV.

Other programs include permanent magnet IDs with enhanced

magnetic designs capable of producing high magnetic field. As

undulators, these devices will exhibit larger photon energy tunability than

current devices. As wigglers, these devices will be capable of achieving

high critical fields above 50 keV.

These special devices are an important a part of the R&D acti_4ty in ID

source development at the APS. It is expected that APS users and scientific

needs will spur activity in other areas of source development after the

storage ring becomes operational.

- 231

-

REFERENCES

[1] Characteristics of the 7-Gev Advanced Photon Source: A Guide forUsers, G. K. Shenoy, P. J. Viccaro, and D. M. Mills, ANL ReportNumber ANL 88-9

[2] Bilderback et al., Rev. Sci. Inst. _, 1419 (1989)

[3] P. J. Viccaro, G. K. Shenoy, S. Kim, and S. D. Bader Rev. Sci. Inst.,_, 1813 (1989)

[4] J. Goulon, P. Elleaume, and D. Raoux, Nucl. Inst. and Meth., A254, 192(1987)

[5] S. Yamamoto, H.Kawata, H. Kitamura, M. Ando, N. Saki, and N.

Shiotani, Phys. Rev. Lett., 62, 2672 (1989)

[6] H. Onuki, N. Saito, and T. Saito, Appl. Phys. Lett., 52,173 (1.988)

[7] P. Elleaume et al.. Submitted to Nucl. Inst. Meth.

[8] B. Diviacco and R. P. Walker, Submitted to Nuclear Inst. Meth.

[9] K.-J. Kim, Nucl. Inst. Meth., A24(_,425 (1984)

232

ADVANCED PHOTON SOURCE

OUTLINE OF PRESENTATION

• Insertion Device (_D) SynchrotronRadiation

(General Features)

• Expected Spectral Properties Of APSSources

• Relevant R&D lD Prototype Results

• Special Purpose lD Sources For The APS

233


BEND MAGNET

Ikl

[3 - _ ..... 2vi'

Vertical Opening _I'- 1/T

Angle ............ --

7- 1957 ER

At 7 Gev, 1/7 ~ 0.07 mradBeam Height ~ 8 mm at 50 m

INSERTION DEVICE (Hybrid Permanent Magnet)

N S N S N S N S N_Mag netsm!_,,._:m_:'=':_*_::i:_:_...':_B%m_i_:_i_i-m_ P 01 e s

mm mm I N I l mm_ mm m

Mi ..mm m m..._Im_ ma mm mm

S N S N S N S N S

Particle Radiates at Each Lobe of Trajectory

234


TYPICAL STRUCTURE OF HYBRIDPERMANENT MAGNET INSERTION DEVICES

_'0

Vanadium Nd Pe B

permendur permanentpole pieces magnets

B = g0 cos(2=z/Xo)

Bo(T) Peak Field at Poles

XoK

Z

PARTICLETRAJECTORY DETERMINESDEVICE CHARAOTERISTICS

235


PARTICLE BEAM TRAJECTORYXcK

×

DEFLECTION PARAMETER KK = 0.934 X0(cm) B0(T)

CENTRAL RADIATION CONE

ANGULAR WIDTH ~ 1/?

? = 1957 ER(GeV )

WIGGLER REGIME

K>>ISUM INTENSITYFROM EACH POLE

UNDULATOR REGIME

K-_IINTERFERENCEEFFECTSWITHIN RADIATION CONE

236


UNDULATOR SOURCES

INTERFERENCEEFFECTSINUNDULATORREGIMECAUSE FREQUENCYAND SPATIAL 'BUNCHING'

EXAMPLE: APS@ 7GeV 100mA

ON-AXIS FREQUENCY DISTRIBUTION

= 237

z

ADVANCFD PHOTON SOURCE

UNDULATOR RADIATIONSPATIAL DISTRIBUTION AT ODD HARMONICS

. ANGULAR WIDTH OF CENTRAL RADIATIONCONE FOR ODD HARMONICS .n =1,3,5,...

Gaussian Central Cone Approximation.

G'R - _/Xn/L =(l/y)_/(1 , K2/2)/(2nN)

• SOURCE SIZE_m

4ZC_R= _/XnL Zn = Harmonic EnergyL = lD Length

238

(_PeaLU/N_>t)d


GENERAL SOURCE PROPERTIES

Particle Beam Emittance Effects

• Radiative-Single Particle

Source Size: _ r

Source Divergence" _'

• Particle Beam Distribution

Beam Size: (_p• 0 .1Beam Divergence, p

• Effective Source Size and Divergence

Size:

= _/(Or2 + Op2)Divergence:

--- j)

' _ ' 22= _p)

240

,, ADVANCED PHOTON SOURCE

UNDULATOR RADIATIONParticle Beam Emittance Effects

• Typical APS Particle Beam ParametersBeam Size And, Divergence

, i ,=,,,

(_v vox Oy x o y,

I (_m) (_m) (_rad) (_rad)

Bend 1 1 5 1 1 0 63 7

lD 3 1 0 85 24 9

• Typical Undulator Single Particle (Zero-Emittance) Radiative Source Size AndDivergence

1st Harmonic at 10 kev

Length, 2.5 m.

_r = 25 gm O'r-- ~10 grad

(Brilliance) (Brightness)(1/y = 73 _rad)

_

241

ADVANCFD PHOTON, SOURCE

SOURCE BRILLIANCE

- 1Extended Pinhole DetectorSource ,.

Flux Through Pinhole Depends on BOTH

Angular Divergence andSpatial Distribution

Brilliance (Brightness): On Axis (Peak)

g "_ F i(_.,__'_ _) F=motai Flux,_ _ _

Angular Flux Density:

242

ADVANCED PHOTONSOURCE

.,GENERAL PURPOSE IDs

Undulators WigglersA B A B

Period (cm) 3.1 2.1 1 5 2 5Length (m) 2.5 2.5 1.5 2.5

Fundamental"Min (keV) 4.5 1 3Max (keV) 1 4 2 0

Ec(keV ) 32.6 9.8

Kmax 2.5 1.1 14 7

UND A & B, WIG A:Permanent Magnet (Nd-Fe-B) HYBRID DEVICES

WIG B"Electromagnet

Bending Magnet Radiation" Ec = 19 5 keV

: 243


APS BEND MAGNET

Ec = 19.5 keV

1016 _ . ,,, , ........., , , ,,,,_ ' ' ' ' ' ' ''I • ' ' ' ' l

b..

oJ

10 14 J...----'__...---'- ,,. ,,,,.,,r %%omp_jf %

I,-4 •

E 13"_ 10 ",= 1,,,,,

t .

,..-, 10 .. , -

,, APS (7 GeV, 100 mA) '1 1 '

10 .......... NSLS (2.5 GEV,500 mA)' i

Q) I •

= 10 ' '10 "" ' "

m F10 9 , , , , , ,,,,I , , , , ,,,,i , , , o.,,.,

.1 1 10 100ENERGY (keV)

Brilliance ot gending-Hagnet Radiation from Various SynchroLron Sources

m

244


UNDULATOR RADIATION

• ENERGY TUNABILITY (nth Harmonic)

2En(keV) = n 0.949E R

X0(1+K2/2)

K = 0.934BoX 0

B0 = Peak Magnetic Field (T)

X0 = Undulator Period (cm)

ER -Storage Ring Energy (GEV)

. ENERGY WIDTH OF HARMONIC n(Zero Emittance)

AE/E = 1/(nN) N = Number of Periods


APS Undulator A (,3.1 cm Period)1st Harmonic Tunablity

On-Axis Brilliance of the First-Harmonic Radiation from APSUndulator A at 7 GeV and i00 mA (The first-harmonic peaks at various energies

are obtained at magnet gap settings of (a) 11.2 mm, (b) 13.9 mm, (c) 16.5 mm,(d) 19.7 mm, (e) 24.7 mm, and (f) 30.1 mm. These calculations include thephase-space dimensions of the positron beam.)

247


Undulator-Wiggler lDPeriod=8 cmDeflection Parameter K = 0.934 BoXo

1_<K<9

250

i

252

ADVANCED PHOTONSOURCE

Wavelength, nm124.0 12,4 1,24 0,124

102° J I I I

,- -, ,,,,7-GEVUndulator%

,._ 018 1-2-GEVUndulators S _ %"1 - ,_ ,_ _

_' NSLSXl %

APS _,rn I _ Prototype '_

,_., 1016 / 7 GeVWiggler _ ,,- "' "" "',. _%0 .,.." "' PEP Undulator _

¢,,II

E

1014 -EE

m

T

1012 -r-O

.l.,,,,t

Ot..-13. Tantalus

_ Copper K Molybdenum Kt..)

- r- 10l°,-lau

'r" Copper L

-- um K1,,,.

= ,_

o 810 - Carbon Kr_ Bremsstrahlung03 Continuum

106 ! I10 -3 10 -2 10 -1 1 10 10 2

Photon Energy, keV

- 25 3


APS STORAGE RING TIME STRUCTURE

• Ring Circumference: 1104 mOrbit Period: 3683 nsNumber of Bunches 1 - 6 0Bunch Duration 50-100 ps

• Flux (Number Of Photons) Per Bunch7 GeV, 100 mA20 Bunches Circulating

Source Flux (x-rays/0.1%BW)

Bend 1.7 x 106 /mrade

Wig A 4.0 x 107 /mrade

Und A 2.1 x 108

Bend and Wig at EcUnd A At 1st Harmonic

254

ADVANCEDPHOTONSOURCEul j iii i li i i ii i

INSERTION DEVICE TECHNICAL DESIGN

Based on R&D Effort

• APS/CHESS Prototype Undulator A- 3.3 cm Period- 2 m Length ( 123 Poles)- Specification of Device: APS/CHESS- Constructed by Spectra Technology,

Inc.- Installed and Tested on CESR/Cornell in

Low Emittance Mode, May-June 1988

o APS Prototype Undulator for the U-5 Port/VUV Ring _..:_tthe National Synchrotron LightSource

- 7.5 cm Period

- 2.3 m Length ( 55 Poles)- Specification/Preliminary Design

- of Device: APS

- Constructed By Spectra Technology, Inc._ - Completion: February 1990- - Installation: April 1990

SHIPPED TO NSLS' MONDAY, MARCH 5, 1990!

255

ADVANCEDPHOTONSOURCE

APS/CHESS PROTOTYPEUNDULATOR A

MAGNETIC FIELD ANALYSIS

Specified Measured, , i

Period (cm) 3.3MinimumGap(cre) 1.35MaximumField B(T) 0.45 0.53

(AB/B)rms(%) < 1 0.3Transverse

Rolloff(%) <0.5 0.2Steering

Erro r(G-cm) <100 <100 ,,,,

• No Measurable Effects on CESR Storage RingOperating in Low Emittance Configuration

° (AB/B)rms Satisfies APS Requirement

256


APS PROTOTYPE UNDULATORGAP TAPER

![111[iIlIlIIl!].JlIEll'I,'i"-I[IlIJiI_'le + .6

ELLiItLUZI_q .iIIi Iii II

Broadening of Fundamental versus Gap Taper

258

:

i


1.00 , , r , 1 ' r" , , | , , , •

_>-o.75 __. "_

o -- o.o0.50 t.... .

__ \_ _ k\ ---- AG-1.27mm

rr" 0.25 " /" " \\ \ \ °

0.00 , I t ' I • , , ;6.0 6.5 7.0 7.5

Photon Energy (KEV)

Broadening of fundamental peak vs. taper in gap.

• I-- " I " "'_l" '_' I " I " I " I 3-- I "

40 ". _

._o_ 30EC

_-- 20>

rr 10 _.,.,.-_"""/_ .

• u

0 , I , ! , I , I , I , I I | I I •

= 6.4 615 6.6 6.7 6.8 6.9 7.0 7.1 7.2 7.3

Photon Energy (KEV)

= Manganese transmission spectrum obtained with radiation from

the undulator at a fixed gap tapered by 2.54 mm about a 2.1 cm average.

= The sudden decrease in transmission represents the Kt, absorption edge

and the ripples immediately above it are from EXAFS.)

- 259


U-5 UNDULATOR CHARACTERISTICS

• Mechanical Structure:- C-Frame Structure- Non-Magnetic Material- Spring Compensation of Magnetic/

Weight Loading- Magnetic Beam Total Deflection

< 0.0002 in.- C-Frame Total Deflection:

< 0.0005 in.

• Magnetic Structure:- Nd-Fe-B Magnets, Nickel Plated- Vanadium Permendur Pole Pieces

260_=

-- /_0/-_


TECHNICAL DESIGN OF SPECIAL PURPOSEINSERTION DEVICES

Major Thrusts in R&D Effort Related tolD Technical Design

• Devices with Higher Peak Magnetic Fields atSmall (10-12 mm) Gaps. IncreasedUndulator Tunability at a LargerMachine Aperture.

- Wedge-Pole Design- Designs with Enhanced Flux Returns.

• Devices for Producing Variable PolarizationX-Rays.

- Hard X-Ray Energies above 8 keV'Elliptical Motion Multipole Wiggler.Slow Modulation of PolarizationPossible

- X-Ray Energies below 8 keV:Crossed Field Undulator. Rapid (10 Hz)Modulation Possible.

Conceptual Designs and Performance Evaluationof Devices are Under Way.

264


POLARIZATION CHARACTERISTICS OFSYNCHROTRON X-RAY SOURCES

• Bending Magnet

On-Axis Plane Polarized (o)ini

Horizontal On-Axis PlaneOff-Axis" Both (; and

° Planar WigglerPositive and Negative Lobes of TrajectoryCancel _ Component.

Plane Polarized

• Planar Undulator

On-Axis' Plane Polarized (o)inHorizontal On-Axis Plane

Off-Axis" Both o and

(Complex)

--_ 265

-t_


BENDING MAGNET POLARIZATION

e-t-ELLIPTICAL

4, _ (+)

LINEAR (5

ELLIPTICAL(-)

, PLANERWIGGLER OR UNDULATORV

k

X

_ LINEAR

I

CURVATURE _ LINEAR

266


Elliptical Motion Multipole Wiggler

Bx ~0.1 T

' .__, By ~ 1.0 T

Crossed Undulator(K.-J. Kim-LBL)

267


ELLIP FICALWIGGLER

By

_ Elliptical'Trajectory

_- -_ Bx Depends on Phase ofBx and By

Trajectory + ,'m

r

,."_

/t q

J, Elliptical Polarization"_" / /,1

, On-Axis,di .°

n-Bending Magnets

/ I

Change Phase by Shifting Bx wrt By

268


ELLIPTICAL MULTIPOLE WIGGLER

4 i',_lll =-"

Cu Attenuator Wiggler-

'}'/(Kx/?)

1.07 11 21

Degree ofCircular o

Polarization.. _+-'__--_c--_-1.0 L 1 I

1

RelativeIntensity I(5_-

IGz _

1(53 ,0 I 2 x104 rod.

= Vertical Angle

(x10"4 rad)

Adapted from S. YAMAMOTO et al.Phys. Rev. Lett. 62, 2672 (1989)

]1

269


Undulator Polarization Properties(Zero-Emittance Case)


Undulator Polarization Properties(APS-Emittance Case) 1st Harmonic

1019 ...... _.,,' 1 ' "°1 ' I _ I ' i ]

'4

_, __ 1018

m 17• _ 10 -"

,

,= 10 76:

o,-.:.= 1015

.J

: f1014 I [ ! ' _ I 1 I l l 1 li

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

, Horizontal An__Ie(mrad)101_ ' 1 _ I ' _ , l ' i' '

,, _s_A:.,7:- _ _.o-.- ,,",,: 7 _o

_> ;o _/ ', / t ; ',,_

o- 1016 /",,,

_- 15 ',

:_" ]014 " '

"=_: 10 13

'"_ "_ t ; yI0I-'_ ' ' : I ' I ' t ' I

-0.3 -0.2 -O,i 0.0 0.i 0.2 0.3

= Ver_Jcd Angle (nn_r-ac)_.....al

-= 271

'" lll_l' ' 'N ,r - ,r lit r,i I_,_ _,_,_,, II ..... III 'IPl_' pr,li ,I1,_

"Can a Powerful Source (APS) Cast Useful Light on Atomic Hole StateProcesses?" P. L. Cowan, Mar. 30, 1990.

Al_hough the workshop is olficially on the subject of Atomic Physics, it has

become customary to link Atomic, Molecular and Optical Physics into one

package. Since the issue under discussion is, "What can be done with the

APS?" one can argue further that ali experiments will use x-rays in one way or

another and therefore could be categorized as X-Ray Optical Physics.

A superficial case for unity can be made from Figure I. The top spectrum is a

Fano shaped multivacancy resonance in the x-ray absorption spectrum of Ar gas.

The lower figure shows a measurement of the x-ray absorption spectrum of C]

adsorbed on a Cu(O01) surface. In both cases similarly shaped spectra are

observed, but in the second case the resonance is due to the collective

scattering of the incident x-rays by the substrate crystal (i.e., a

Cu<lll> Bragg reflection). The latter effect, known as the x-ray standing

wave effect, is useful for surface structure determination, lt is important

to remember that atomic effects like in the upper figure may influence the

optical effects such as in the lower figure.

Continuing the argument for Optical Physics as a unifying endeavor, I have

listed in Figure 2 a number of properties of x-rays (or photons) along with

types of experiments where these properties play a central role. One can

argue that the first four properties are aspects of the same thing, but the

fifth, polarization, provides a totally independent parameter which is

beginning to play an important role in our studies.

[-q

272=

_

In our studies of atomic hole processes at the NIST x-ray beamline, X-24A at

the NSLS, we control and measure x-ray energy and polarization. A schematic

of the instrument used to do this is shown in Figure 3. X-rays from a bending

magnet at the NSLS X-ray Ring are filtered in energy and their polarization is

refined by a tunable two-crystal monochromator. The target, which can be

either a solid or a gas cell, is then observed by a curved single-crystal

spectrometer which also can perform polarization analysis. In some

experiments the observation angle, B, of the spectrometer with respect to the

incident polarization can also be varied.

This arrangement of an primary monochromator and a secondary spectrometer

enables "double spectroscopy." The significance of the two photon energies,

_i, and _m2, is spelled out in a Kramers-Heisenberg expansion of the photon

scattering cross section as listed in Figure 4.

In the case of resonant x-ray Raman scattering it is the middle term in the

Kramers-Heisenberg expansion (enclosed in the box) that dominates. The matrix

elements are related to the x-ray absorption and emission transitions

probabilities. I_ one assumes the matrix elements associated with emission

z are insensitive to the excitation energy, the resonant Raman process can be

modeled by first fitting an empirical model to the x-ray absorption spectrum,

then using the derived parameters to match the Raman spectra recorded at--i

various excitation energies. The next several figures (Fig. 5-9) show the

obtained fit to the absorption spectrum and several Raman spectra. Perhaps-

the key feature of these spectra is the narrowing of the emission features on

J

q_ 273

resonance. This indicates that "lifetime broadening" can be avoided so that

even at the higher energies to be obtained at the APS high resolution spectra

may be obtained.

The Kramers-Heisenberg formula can also apply to resonant elastic x-ray

scattering. In this case both of the first two terms are significant. We

became interested in the polarization dependance of the elastic scattering

since this has implications for the optical properties of materials at

resonances. Our measurements of the polarization of the elastic scattered

x-ray observed at 90 ° scattering angle for polarized incidence are shown in

Figure I0 as a function of energy near the CI K-edge for CFCI 3.

While the elastic scattered x-rays, which are normally polarized for 90°

scattering, become depolarized, the x-ray fluorescence, which is typically

unpolarized, can become polarized. As shown in the overlay, this polarization

of fluorescence (or Raman scattered) x-rays, is different for emission

involving molecular states with different symmetry. A schematic explanatiol

of this effect is given in Figure ii. For resonant excitation with polarized

x-rays, the excitation probability can be a strong function of the orientation

of individual molecules. The subsequent fluorescence from the resulting

assembly of aligned-excited molecules will then be polarized as indicated in

the figure.

The aligned-excited molecules created as above will also radiate

anisotropically. This effect is demonstrated in Figure 12. The relative

intensities of the spectral components is altered by observing the spectrum

either alopg the polarization vector of the excitation beam (B-O) or at 90°.

274

The above results indicate that to date some success has been obtained in

studying and understanding inner shell hole processes. In each case we have

extemded the traditional techniques of x-ray spectroscopy by utilizing the

energy tunability and polarization characteristics of a synchrotron radiation

source. The final figure (Fig. 13) lists a number of ways that x-ray

spectroscopy might be extended further given an increased photon flux from an

advanced x-ray source in conjunction with further improvements beyond our

current state-of-the-art experimental apparatus.

275

Argon (lsSs)4s4p Resononce

III

E •0

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285

GAS PHASEX-RAYPOLARIZATION

Absorption C• • 0 •

C .. ,,,""h=" "OI"I

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°° CC ._i ,,:_, ..

• •

"Oi"• •

• m,b

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Anisotropic angular distributions of CI K-V x-ray emission

from resonant ly excited CF3Ci molecules

i

i

i

FUTURE EXPERIMENTS

Oriented molecules:

Surface adsorbate

Chiral molecules (circular pol.)

Molecules in solution

Clusters

Interfaces

Coincidence

Pump/Probe

Quadripole effects

Vapors (open shell atoms)

Studies of Free and Deposited Clusters using Synchrotron

Radiation

W. Eberhardt

Exxon Research and Engineering Co., Route 22E, Annandale NJ 08801, USA

Abstract

Clusters deposited onto substrates or into rare gas matrices are beeing

studied at present synchrotron radiation sources using absorption or

secondary emission type spectroscopies. Thus the electronic and geometric

structure of these systems can be determined as a function of particle size.

Using the next generation synchrotron radiation sources, it will be possible

to extend these studies to free beams of these particles where the results

are not perturbed by substrate or matrix effects.

290

.

I_ntroducti0n

Clusters of atoms form a new class of materials to the extend that their

geometries and properties, like for example the electronic structure,

chemical reactivity, or magnetic moment, are distinctively different from

both the isolated atom and also the corresponding bulk materials

Synchrotron radiation related techniques like absorption (yield)

spectroscopy, EXAFS, and photoemission are ideal techniques to probe these

properties. This has been accomplished in the past for clusters deposited in

a matrix or on various surfaces [1-4], whereas for studies on free cluster

beams are mostly performed using lasers or other laboratory light sources.

To date only very few experiments have been reported on free clusters using

synchrotron radiation [5-7].

Most of the laboratory experiments performed on clusters to date are

based on laser ionization and mass spectrometry. In general, these studies

yield insight into chemical reactivities and the formation and stability upon

ionization of the clusters. The ionization potentials for the clusters as a

function of size can be approximated by using different laser wavelengths

for the ionization in these mass spectroscopic studies. However, more

fundamental characteristics like the electronic structure and density of

states or geometry of these new materials have not yet been determined for

a wide range of cluster species and sizes. Only for some diatomic and

triatomic species resonant two photon laser ionization could be used to

determine the electronic states and also the geometry via an analysis of the

vibrational modes [8].

- Compared to these laboratory sources, synchrotron radiation offers some

unique capabilities to study clusters and answer some of the fundamental

questions about their properties, provided the cluster source and the

i

29t

l

characteristics of the photon beam can be matched to give enough intensity

for these studies. While bending magnet radiation can be used in some very

favorable cases [3-6], the enhanced flux from an insertion device will be

needed to perform these experiments for a wide range of materials [7].

Experimental Tec_hniaues

Yield spectroscopy has been used in the synchrotron radiation community

for about two decades to study the wavelength dependent absorption of

materials. For deposited mass selected samples the electron or

fluorescence yield can be measured to determine the absorption as a

function of photon energy. Whereas for a beam of free clusters mass

resolved ion yield measurements can be performed, using a time-of-flight

mass spectrometer, offering the additional advantage of a parallel detection

scheme. These studies, performed around and above various absorption

edges, will give insight into the unoccupied electronic states (NEXAFS) of

the clusters. Moreover, as equivalent studies on molecules have shown, not

only electronic structure information can be obtained in this way, but also

some of the features in the spectra, like shape resonances, are indicative of

_nd related to the geometry of the particles. At least for some of the

smaller cluster species the geometric structure may thus be deduced also.

In addition, high resolution near edge spectra for molecules exhibit

pronounced vibrational substructure. Taking these high resolution spectra

for clusters will allow us to determine the fundamental, optical active,

vibrational frequencies. In addition, through an analysis of the

Franck-Condon factors of the vibrational progressions the electronic

bonding of the clusters can be investigated.

Extending these measurements several hundred electron volts above the

292

absorption edges the EXAFS signal may be obtained, which is directly

related to the cluster geometry since its origin is in backscattered wave

contributions to the wavefunction of the photoelectron from the nuclei

surrounding the atom where the absorption occured. Parameters like the

backscattering amplitude and the phaseshift may be readily obtained from

EXAFS studies of the corrspcnding bulk materials. Thus the analysis of the

cluster EXAFS signal sholJld yield the nearest and possibly next nearest

neighbor distances as well as the average coordination number for an atom

within the cluster.

The occupied electronic states of the clusters can measured in a

photoemission experiment, where the energy of the emitted electrons for a

fixed photon energy is analyzed by an electron spectrometer. On deposited

mass selected clusters studies of this kind are currently underway. For

beams of free clusters this data can be obtained in a coincidence

experiment, where the photoelectron kinetic energy and the mass of the ion

produced are determined simultaneously. Another, less efficient, approach

is to study the photoemission of a beam of mass selected ionic or

reneutralized particles. Spectra of the valence electronic states will

z answer fundamental questions about the development of the electronic

structure of a solid as the particle size is varied. Core level spectra give

insight into dynamic processes like charge transfer, hybridization, and

screening in these particles. Possibly we can also use these studies of the

microscopic electronic structure to enhance the understanding of +he

- development of maceoscopic properties like electrical conductivity,

magnetism, specific heat, or chemical reactivity of the clusters.

293

..... j...... _j,, r_,Jil Illl'

Cl_ster Source and Intensity Considerations

The cluster sources currently in operation can be devided into three major

categories. Clusters are produced either by laser vaporization, sputtering or

by aggregation of atoms in a vapor. Laser vaporization is probably the most

commonly used source for clusters [8]. Vaporizing a material by a focussed

laser beam into a high pressure carrier gas and subsequent expansion

through a nozzle and cooling is a very convenient way to make clusters of

almost any material. The major disadvantage of this kind of source, with

respect to experiments at a synchrotron, is the rather low repetition rate of

the most commonly used vaporization lasers (about 10 Hz). Even though

higher frequency lasers could be used, it will be difficult to raise the

repetition rate above a few kHz and thus this source will always be ill

matched to the high repetition rate (MHz) of the synchrotron radiation

pulses.

Oven (aggregation) sources can be built to produce a continuous beam of

cluster particles [2,6,7,9]. The material is heated until its vapor pressure is

at least a few Torr but more often the stagnation pressure is held near one

atmosphere. The clusters are formed within this atmosphere through

collisions and aggregation of atoms. Most commonly an inert carrier gas is

introduced into the oven also. Adiabatic expansion through a nozzle produces

a continuous cluster beam, whereby the distribution of particle sizes can be

controlled by changing the aggregation and expansion conditions of the

source.

In the third kind of source the clusters are produced from a solid target

by sputtering it with an ion beam of 10 to 30 kev kinetic energy [1,3]. This

source, coupled with a quadrupole mass spectrometer or a Wien-filter

produces a very intense beam of mostly smaller clusters. If a quadrupole

294

spectrometer is used to filter the clusters this source is ideally suited to

deposit mass selected clusters on substrates. The intensity of the clusters

is very high and the kinetic energy can be controlled sufficiently well to

achieve a "soft landing" [3]. Compared to the other sources, the clusters

produced by sputtering are "hot", i.e. they are not at thermal equilibrium and

carry a large amount of internal energy.

As already mentioned above, studies on deposited clusters, even combined

with mass selection prior to deposition, are being performed on present day

bending magnet synchrotron radiation sources [3-5]. Experiments on free

clusters have been carried out using bending magnet radiation, but these

experiments were performed on a more or less narrow ensemble of particle

sizes [6]. To my knowledge, the only experiment on a free cluster beam with

monoatomic mass resolution was carried out for Hg clusters produced in an

oven source using a VUV undulator source for the probe beam [7]. This

establishes a proof of principle, that VUV absorption studies (ion yield

spectroscopy) can be performed when the appropriate cluster and light

source are coupled.

On the next generation synchrotron radiation source these experiments

can be extended to other clusters, which are less copiously produced than Hg

or alkali clusters [7,9] and photoemission as well as ion yield studies can be

performed. Rather than crossing the cluster and photon beam, the signal

rates may be substantially enhanced in a colinear beam geometry, similar to

the experimental arrangement used for the studies of single atomic ion

species reported in the literature [10]. Performing EXAFS, NEXAFS, and

photoemission studies not only on neutral clusters but also on cluster ions

= will, among other information, confirm or disprove geometry changes, which

are predicted by theory to occur for quite a variety of cSuster species upon

295

ionization.

Comparing the quadrupole monosize cluster ion source [1,3] with the

source used to study atomic ions earlier [10], we find that both ion beams

have quite comparable ion densities and beam dimensions in the interaction

region. The cluster source delivers a cluster ion current of several nA at 10

eV mean energy, whereas the atomic ion source delivers up to 100 nA

current at a much larger beam energy of 1 to 4 keV [10]. Thus overall the

experiments should have comparable intensities. The atomic ion experiment

was carried out with a typical photon flux between 109 and 6x101 0

photons/sec, which resulted in count rates of about 100 sec "1. With an

undulator or wiggler source installed on one of the third generation

synchrotron radiation sources, where the photon flux after

monochromatization can be as high as 1012/sec, these experiments can be

carried out even at higher photon energies, where the cross sections tend to

be smaller than in the VUV region.E

With some further development effort on the cluster sources these kind

of experiments on clusters will be quite feasible in the future and they

offer some exciting prospects for synchrotron radiation based research in

the "transition region" between atomic _.nd molecular physics and solid

state materials science.

Ackno_wledgements

I would like to thank D. Cox, P. Fayet, M. Lester, and E.W. Plummer for

many stimulating discussions about the possibilities of performing these

kinds of experiments c,n a synchrotron.

296

References

1. P. Fayet, F. Granze:, G. Hegenbart, E. Moisar, B. Pischel, L. WSste, Phys. Rev. Lett.55, 3002 (198.5)

2. S.B. DiCenzo, S.D. Berry, E.E. Hartford Jr., Phys. Rev. _B38,8465 (1988)

3. W. Eberhardt, P. Fayet, D. Cox, Z. Fu, A. Kaldor, R. Sherwood, D. Sondericker, Phys.!

" Rev. Left. 64, 781 (!990)_n

4. J. Zhao, P. Mor4ano0 M. Ramanthan, G.K. Shenoy, M. Schulze, Bull. Am. Phys. Soc..35, 605 (1990)

5. L. Cordis, G. Gantef6r, H. Hesslich,A. Ding, Z. Phys. D3,323 (1986)

6. J. Stapelfeidt, J. W6rmer, G. Zimmerer, T. M611er,Z. Phys. DI_, 435 (1989)

7. C. Brechignac, M. 8royer, Pi', Cahuzac, G. Delacretaz, ?. Labastie, J.P. Wolf, L.W6ste Phys. Hey. Lett. 60, 275 (1988)

8. For a review see: M. D. Morse, Chem. Rev. 86, 1049 (1986)

9. K. Rademann, Ber. Bu_senges. Phys. Chem. o9._,653 (1989)

10. J.C. Lyon, B. Peart, J.B. West, K. Dolder, J. Phys. _, 4137 (1986)=

297

=

Atomic Physics with New Synchrotron Radia0on:Report from the Japanese Working Group

Masahiro Kimura

Department of Physics, Osaka University, Japan

The construction of a new photon facility, SPring-8, is beingstarted this year in Harima, Japan, and the first photon beam is to besupplied to users in 1998. As a next generation photon source, thisfacility will rely mainly upon insertion devices like the APS.

The source has two characteristic features. One is that the photon

flux is ve,T powerful. In atomic physics target density is often verydilute, and, in many cases, coincidence measurement is desirable to getmore definite conclusions. Only with the advent of an intense photonsource such studies become tractable and will compensate a thin target

density. Another feature is that it can yield photons as high as onehundred or two hundred keV as seen in Fig. I. The lower part of the

figure shows the absorption edges of ali elements. Since the K-edge ofuranium is about 120 keV, the new source can be used to ionize even theinnermost shell of the heaviest element.

Recently the committee of the new facility has decided to installlong-distance undulators in addition to 6.5-m undulators. These 30-mundulators can yield photons of much higher brilliance, or soft x-rays, ofhigher coherency. They may also be used to develop FEL (free electronlaser) in soft x-ray region in the future. Therefore our proposals includethe studies which require not only hard x-rays but also soft x-rays.

In order to discuss the possible projects in the field of atomic

physics with these new photon sources, a group was organized inDecember 1988. Members of the group are listed in Table 1. The groupconsists of about 30 Japanese atomic physicists who have intere_ '' in theresearches with this new facility. Two third of them have expe_t.nceusing existing SR sources.

The following themes have been discussed (multiply charged ion isabbreviated to MCI).

1) Spectroscopy of atoms and molecules.2) Photoionization of ions (inclusive of MCI)3) MCl-trap (spectroscopy of MCI, cold MCI plasma)4) Collisions of very slow MCI5) Electronic and atomic structures of microclusters6) PlasmThe report of the working group was printed last May in Japanese,

and my talk is about its contents.

298

Table 1. Li_t of group n_embers

Y. Achiba, N. Kobayashi, and K. Okuno (Tokyo Metropolitan Univ.)H. Anbe, Y. Awaya, and M. Takami (RIKEN)I. Arakawa, and T. Hirayama (Gakusyuin Univ.)N. Hishinuma (Tokyo Univ.)Y. Itikawa (Inst. of Space and Astronautical Science)Y. Isozumi, and T. Mukoyama (Kyoto Univ.)Y. Itoh (Johsai Univ.)S. Kawatsura (Kyoto Inst. of Technology )M. Kimura (Osaka Univ.)T. Koizumi (Rikkyo Univ.)H. Maezawa, A. Ogata, and A. Yagishita (KEK)T. Mizokawa (Nagaoka College of Technology)S. Ohtani, M. Sakurai, K. Sato, and H. Tawara (National Inst. for

Fusion Science)N. Saito (Electrotechnical Lab., MITI)Y. Saito (Nagoya Univ.)Y. Sato (Tohoku Univ.)M. Terasawa, and T. Sekioka (Himeji Inst. of Technology)J. Yoda (National Res, Lab. of Metrology)

- M. Yoshino (Shibaura Inst. of Technology)

1. Spectroscopic study of atoms and molecules

When atoms or molecules absorb high energy photons, inner shellelectrons are excited or ionized. Inner hole states are generally unstable,and several kinds of ions are finally produced through successive Auger

, decays. Such a process is one of the fundamental processes of interactionbetween high energy photons and matter. In such a study the followinginformation is essential:

1 ) energies of hole states.2) ionization potentials to produce multiply charged ions.

Though binding energies of electrons in atoms and molecules areelementary quantities, it is not always easy to determine the accuratevalues. Particularly those of multiply charged ions wb:,ch are determinedoverwhelmingly from theoretical calculations or empirical laws at the

- present stage. Such examples are shown in Figs. 2 and 3.

299

Regarding inner-hole states, the following topics are considered:

a) absorption spectroscopy -- absolute measurements of photoabsorptionb) photoelectron and Aug_;-electron spectroscopy --energy and angulartkistributions of photo- and Auger electronsc) charge analysis of product photoions and their yieldd) coincidence between ejected particles (electrons, photons, and ions)e) partial cross sections for ionization of inner orbitals as a function ofphoton energies.f) partial cross sections for producing multiply charged ions as a functionof photon energies.g) dissociation after photoexcitation of a specific atomic site in a molecule.h) photoetching and photodesorption from solid surfaces and analysis ofsurface electronic structure.

To give an example, Breinig et al. (1980) measured the spectranear the L-absorption edge of Xe with high resolution and determined the

" hole states of 2s-lnl, 2p-lnl, and binding energies of 2s and 2p electronsas limiting values of these hole states. Such methods can be applied toother atoms or ions.

Another method of study the processes is photoion measurement.Such an example is shown in Fig. 4 which was copied from the work ofNagata et al. (1989).

Not only atoms but ions including multiply charged ions will be thetarget of investigation with the future SR. There exist about 4000 speciesof MCI as shown in Fig. 5. In other words, atomic physics can be extendedto two-dimensional from one-dimensional field, and investigation through

isoelectronic sequences can be performed. Such systematic study becomespossible only when multiply charged ions are made targets.

2. Photoionization of ions

Experimental data of photoionization of ions are very scarce since

a sufficiently high density of target ions is not readily available. In

. particular, no measurements for MCI have been reported so far. Evenemploying both intense SR and ion sources of high density such as ECRIS

will not be enough to measure the processes by using a crossed beam

method. An approach involving collinear interaction of photon- and ion-

beams will have to be applied. This method was employed already by

Dolder's group to measure ionization cross sections of some singly-

, charged ions. In Fig.6 the conceptual experimental setup is shown.

300

The development of high density ion sources and the technique of

beam transport including mergi,ag beam method are essential for this

project. This year we will start research and development of t!,is

technique.

3. Multiply charged ion trap

Ion traps can confine ions of very low-energy in smal! space, and

they are useful tools for making precise spectroscopy of ions. By trapping

singly charged ions a lot of works have already been reported.

In this project MCI are trapped, and sectroscopic investigation of

the MCI and a study on cold plasma composed of MCI are to be

undertaken (Fig. 7). Transition wavelengths among fine or hyperfine

structures of certain MCI get into the accessible region for theconventional lasers. These transitions can also be used for laser cooling of

the trapped _ons.Production of cold MCI is one of the very important factors fox

efficient trapping. For such a purpose, the use of inner-shell

photoionization by X-ray is known to be the best method. The recoil

energies of ions produced by x-ray absorption are compared in Fig. 8

with those produced by heavy ion impact.

For MCI, cross sections of charge transfer with residual gas is

certainly large. We have estimated the lifet;mes of MCI when they are in

the residual gas pressure of 10-11Torr (Fig. 9).

Before storing MCI in an actual trap, we measured, as a test, thecharge distribution of Xe produced through hard x-ray absorption. A

beam of white x-ray from a 5.8 GeV electrons in an accumulator ring in

the National Laboratory for High Energy Physics in Tsukuba was

interacted with Xe gas target. The spectral feature of the photon beam is

shown in Fig. 10. The lower energy side was cut by Be window.

Fig. 11 shows the TOF spectrum observed. The mean cbarge is

estimated as 8.8. This mean charge is compared with the previous

measurements (Fig. 12).

._D.evelopment of a 0he-dimensional ion trapA highly-charged-ion source, EBIS (electron beam ion source) has

been successfully used so far. Constructing a highly charged ion source by

-- replacing an electron beam with an SR beam and by trapping product

ions radially by multipole rf field is proposed. This ion source may be

301

called a one.-dimensional ion trap or photon-beam-ion source, lt can also

be used as a tool for studying photon-ion interactions inside the trap.

4, Collisions of very slow MCI

An MCI has a high internal energy in itself, lt is known that suchhigh potential of MCI manifests its specific character when they areinteracted with a target at as low a velocity as possible.

In our proposal, we prepare low energy MCI-beams of very

narrow energy distribution by crossing supersonic atomic beams with SR

(Fig. 13).

In some cases angular distributions are also investigated.

5. Structure and Electronic States of Microclusters

Though size selection is by far easier for ionic species than forneutral species, neutral clusters are, in almost ali cases, much more

abundantly produced. By using the magnetic interaction between the

field of hexapole magnet and the magnetic moment of clusters, we canmake size selection even for neutral clusters. Methods of XPS or XAFS are

t then applied to analyze those isolated, size-selected clusters (Figs. 14-15).

In our proposal, microclusters are produced by making a pulsed

laser of high power illuminate solid jurfaces. By running through the

inhomogeneous magnetic field, only clusters of certain size can converge

to a given point to be analyzed by XPS or XAFS.

So far is the outli:Je of our report. Our investigation, is focussed

mainly on the processes involving MCI. As R&D, developing the beam

transport and ion trapping techniques of MCI are in progress.

302

SPECTRAL BRILLIANCE

photon energy (keV)

.ol ._ _ lo lOO _ooo...............

I '1020"_ 8 GeV Undulalors(4m)__._,_. 1019 ...... 1 --'--

o"_ 1018 .........................

d |1 7 /

10 - -.... _ L_ "" ""_-,,,,O.,I .,- •

10 1 6 .... .,.--.,_'"'" 8 GeV MPW(2m) %%,,. ,1_

11,-.

E is .........L---""cq .............i, 'T.:_ _ ...............

E 1014 ___ 8 GeV BM(100mA).._X___ -

E :1013 .................

or- 1(.'" ............................................................................................. "- .........................................I:1

= 1010 .... , _, , ,,,,,1 .. • ........ '.., ....... .... ,..,-,,,,.,I , • ....... ,

H _ ! - .., B, ] -"----....._ ......................

,.- ,'o_:,..... m'_r-. ABSORPTION EDGES_6 s -_-.... - Ib-._ _ ........

C" 31 Go -<'3_ S, ",% ]"i_ ._. --

U _o zt li \• -- _3 Ma q/'/ ....E '_ P_ -'I ":'"-, ,"k " l ,'_-- .....

o __ 52 're -ss c, li ',:, 1

- .._--__ _ _ J_..'13__1 I f _-X---- -TT-_,.: '

_ !_ o,I " I ' I 1 k .. ]11_

'g _' • l Iii 1 tX ' lll_

__.____r._ . " 1 Ii '

I i 1

- _oo _o _ o_ A [A]

Fig,l=

.;03

q+K-edge of Fe

E(ls)(keV)ti

O

,

'-

0

0 LO t z (1988)emp i r i c a 1 • o

- Qo

i 0 Manson (1984) e8. 0 Har t ree-Sl a tor

• o- Ib

• lDO

II- • 0

• 0Q 0

Ib 0- _ 0

• 0Q 0

tb 0- Q 0

0_ 0

0 0

- v.o °9°' _ ' I , , , , I , Iq

0 10 2O

Fig,2

304

i |

Ionization Energy of Iron Ions

Spectrum Ground State Ior_izatlon Energy

Conf igurat ion (eV)

Fe I Is22s22p63s23p63d64s 2 5D4 7.870

Fe II is22s22p63s23p63d64s 6D9/2 16. 1879Fe III 30.652

Fe V (2_5.-'_

Fe VI

Fe VII _1 __ 9_88)Fe VIII 151.,061

Fe IX 233.6

Fe X 262.1

Fe XI

Fe XII (._.3_)

Fe XIV __2_._392_-l.'e XV 457.0

Fe XVI 489. 264

Fo XVII 1262.2

r,oxv ,Ir:e xIxFe XX "I_2;9Fe XXJ. _680_-

Fe XXII _799 bFe XXIII i__2_.. "..)Fe XXIV 2045.8

Fe XXV ls 2 1S 0 '_.._82"8.-_..

Ire XXVI ls 2S1/2 92'77.65

from C.Corliss & J.Sugar, J.Phys.Chem. Ref. Data 11,135.(1982)

1

Fig, 3_

-_ 305

Multiplephotoionizationof Cs dme to creationof 4d hole state

partialion-yieldspectra(ion-yieldcross sections)

cs. From J. Phys. B 2__22,3865 (198.9)

10 Z.d"

5/2113/2

2r--_ , _ , , . -_ • ..., ,

2 _- r------_'-" [ " : " I ; 1 " ; 1 _ f &d"_niCs"" I II I ' il

- fE 1

£_ ....... I -" O-g 10 : I ,' I-: ,', I i I '_ I _ I '

: i i - '= "_ Cs: __

" 5 .,,.,r'-o

-6 10 ._o

0 : 10 II,..

L. Cs"" _-3

2 _.0-I 5I

0 , i , ! 0 . I , . , ,----,l ..... _ T---':, ......r- ,70 90 110 130 150 170 190 76 78 80 82 84, 86 88 90

Photon energy (eV) Photon energy {eV)(ai (bi

306

50-

mu] t icharged ions

-

z I .... ,,, ,, ,,,, neutral atoms• 1 50 92

__ atomic number

Fig,5_

307

.

Aq'2

j __i/--j_ SR Dumper

I-t:1s i n gl e b u n c hbeam ,if necessary

,. _-----_-- ECR Ion Sourse

Apparatus for measuring photoionizationcrosssetcions of MCIwi t h ine r gin g bean, ine tho d

308

Experiments with MCI Trap

i) High resolution spectroscopy

Doppler-free LIF

-> QED-term of hl.gher order, nuclear structure

El-allowed transition;,

separation of energy level,s _,2Z 2

lifetime _ Z -4i

El-forbidden line; e.g.,

2p 553 nmAr X 2s22p 5 2PI/2 - 3/2

_ 3p 692 nmAr XI 2s22p 4 3P 1 22p 442 nm

Ar XIV 2s22p 2P3/2 - 1/2

2) Study on cold plasma

High Coulomb interaction -->

Collective motion or phase transition of ion cloud

parameter [-" = (q2/a)/kT, where

4/3)'[a3=fl -1 _)' density of ionsJ

at I-":155 liquid _ solid

309

_, [, ShOrT et cit, CI'_Sg)

10 I I I i I ' I' 1 I 1 I ....

,

:_ J'1_mmeF01r. I -

cW

.,-i 23 MeV C15t0U

CC

-_+ o. 1 - s_lpel_. -CT

c_<_ SSRL X-rays

0.01 - ' I .... , I . _, I__L____I ,_ I ,0 2 4 6 8 10

Ar Charge q

Fig,8

310

Lifetime of multicharged ions (Aq+) in ion trap

Assumptions for estimation:i) lifetime is determined solely by charge

transfer reaction with residual gas;"c= (g nv)-i

• 2) charge transfer _;C_q, q-l=2.48 x lO-15ql. 17 [eta2]

2) ion temperature; T = 0.1 eV/n3) residual gas pressure; p = 10-11 Torr

q _ q, q-i (cm2) -K ( sec )

5 1.6(-14) 430i0 3.7(-14) 19020 8t3(-14) 8440 1.7(-13) 40

: Fig,9

311

| | ' "_ I I I I

10'_. _ GeV

lo _Qtj')¢-

_ -0

,- Oa

-_o_ Xe IL-. K \\ _, , ..i_ ! \\I I l , I --

10 10 2 10 3 10 4 10 + 10 6

Photon energy (eV)

Fig,lO

312

, ,_,o.... +n,

8 - , ....T _t _ -

1 0 t I

Vt

i tt6t2 ,z+ -

, 800 1000 1200

Channel

Xechargestate distribution followingL-andK-sh_,llvacancyproduction,

: Fig,ll__ 313

315

=;

I ' III''

' SR beam

' \ 1I 6-pole magnet \

e tuster I , , \ r" "t_" photoelectron/

i

Apparatus :for studyingslze-selected m.l. croclusters

Fig,14

316

Laser

r

_:: E H

L 1

I

! '' I

!

. __.L

" Clustersource

Laser A. target(solid)B" channel

: C" target ,, upportD' carrier gas supply

___ F' pulse motor

' i:..... II' chamber for size selection_::/. //h .> i/ :._.,:

- </_>><_:.. ,.,_/ ":':__

/.-.//•/I, "/ _\\ \ \ \\_-.t_//-.//'./-- / -///// ._.. B

,, D [

: Fig,15B17

Argon-Ion Charge Distributions FollowingNea,r-Thrcsllold Ionization

Jon C. Levin

l)cpartmcl_t of Phgsics, lhliversity of Te_ncsscc, lO_oa'villc, TeT_nesscc37996-1200aT_dOat" Ridge Nolio_al Laboratory, Oal_'Ridge, 7'e._lllessce37,5'31-6,']77

\¥11en an atom is photoionized in an inner sllell, there are two tnecha.nisllls bywhich tlle remaining electron cortege relaxes to fill the vacancy: x-ray emission andradiationless Auger and Coster-Kronig transitions. In tlm former, the inner-shellllole moves to _ less tightly bound orbital wittmut increasing tlle number of atomicvacancies. In Auger processes, however, the energy liberated hs' t;ranslk_r of a. less-tiglltly-bound electron to the inner..shell vacancy is transferred to another electronwhich is ejected into the continuunl. In this case, the charge on the residual lollincreases by one. Through a series of radiative and non-radiative processes, tlleinitial vacancy 1)ul)bles tlp until all vaca,ncies arrive at the outermost shell, l)ue tothe many possible routes by which this may occur, there can be a broad distributiollof residual ion charge states characteristic of the decay of a. single inne>shell x,aca1_cy.

There have been several measurements of ion charge distributions following inner-sl_ell photoionization. Using photons from x-ray tubes to produce K vacancies in ar-gon well above a.bsorption edges, Carlson and l(rause measured'the resultant chargedistributions with. a magnetic a,nalyzer. _ More recently, Tonuma et al have usedtime-of-flight techlliques to measure charge distributions of xenon ions resulting fromsynchrotron-radiation photoioniza.tion of I, t2a electrons. _"The results showed a. clea.rdependence on photon energy and L-subshell ionizal, ion tllresholds.

Both Carlson and Krause and Tormma el, al made comparisons of tlmir mea-surements wltl_ tlm resul!,s of Monte-Carlo simulal, ions of charge distrilmtions. The['ormer autlmrs used published radiative a,nd nonradiative transition prol)abilities and,in addition, included estima,tes of shakeofl" calculated in the sudden limit. The re-cent simulations of Tonuma et al employ more accurate ca,lculations of radiative aa.nd nonra.diative 4 transition probabilities and the sudden-approximation estilnates ofC,arlson and Nestor. 5 13oth calculations show general agreement with tlm data.

A number of effects have been omitted froln botll theoretical treatments, llow-ever, .As the atom mltoionizes, outer-shell electrons see a reduced nuclear screening,

- resulting in increa,sed binding energy. As a result, some clla,nnels ma.y become closed.1)ecay rates change as tile supply of oute, r-sllell electrons is depleted. Well abovethe plmtoionization tllreshold, tlm sudden-a.pl)roximation ca.lcula.tions of Ca,rlson andNestor provide a. good description of shakeoff. As the mw.rgy of the photoionizing xray api)roaches tlu'esllold from above, the low-energy photoelectron reina.ins in thevicinity of the atom when the inner-shell hole decays, a,lld in this regime, the two-stepexcita,tion-decay pictllre is not va,lid. The t]lreshold energy dependence of sllakeo[l"tlas been measured by Armen el, a,I6 and was found to rise gradually as the high-energy a.symi)totic limit is approached. Tllese effects ali contribute to _ complicat, edion charge distribution which is strongly photon-energy dependent. The differencesbetween theory and exl)eriment are typically small for low charge st,a.l,es for whichonly a few processes colltribute. The production of very high charge states of, e.g.,xenon, can occur by a large variety of channels and for tllese charge sta,tes theorytypically overestimates their relative l)rol)abilil,y, r

318

17Jeca.use so malz$, processes c_m contribul, e to eat;h cha,rge si,a,te, ii, is difNcult, to de-l,ermiiie l,lle e ffecl, ot' ca.cii by ex;t]nining i;lle l,ol.a.l ion ct!a.rge distribut, ion; \lie. t.ot,a l-ion<.:]large disLribut, ion represelll,s aal a.verage over lna.ny effects. 'I'o overcome this l imit.a.-l,ion, we ha,ve recerll,ly lllea,sured argon-ion product, ion as _ t'uncl, iorl of I)otli plio!;oliCllCTg): and Allger doc.a,yciia.niiol following photoioiiiza.l;ioli of I(-shc'll electrons wit.lihighly rl-lorlocllrorllatic SyllCllrol, rori rltdia, t;ion. When l-nt:h.suro.d 'difli:'reilt.ia.l in tlecaycliamiel, the ion charge disl, ril)i.ltioiis are grea.tly siml)lifie.d. Aria,lysis, iii progress,of l,llcse simplified distribul:ions will l)erlnil, ext,ra.ct,iori o17infol.'ma.t,ion icl:)oilt, i'<;lat,ivc,<lecay rat,cs a.nd slia.keoff eft'ect,s t,}la,l; is obscured in l,he singles sl)ect,r_.

\_:lloli llorl-l-lalizcd 1,oCOll,<.;t,a.lit;l)llol, oli flux, st)rim illl;er(:si, iilg t,lircsllold c,ft't,,.<'l,sca.l-i])c. sc(211iii {,lie c.linrge <list:1"il;_ul,ions Fl?c_q.sur(;(lcoincident witli K-I,.,:_L,>:_ktig(,r (l(_-cla.y. Siiic.e virl, ua.lly a.ll 1;,_:_\,icca.ncies deca,y by L-MM Auger t,r&llSit,iOilS>_:l.rgOllioilssl:lotil_l lit, pro,:l/lced 1)rt.'.doriliril/n{ly in c]lnrgo sl;a.l;e4+. Well a.bove l,]lr('s]loid t,ilereis_ lll n.ddit,iorl, a sul.>st,a.nl,ial COliipolielll, Of Ar '_+ resllll, ing J'rol!i slia,kcoff a,il<l I,-MMMdoul_le-kllger processes, kt, cliergies several hurldrecl e\/ above t,lie I_ pliol,oicJliiza,-

-= (,ioil t.llreshold,, i,lie Ar <_+i.o Ar 4_-r&t,io )l_./.sreached _l,llas.$:i-npl,oi:,ic valine of _ 0.5. alarge colIll)oiJell{ of AI 'a+ is evi(ielll, il.l file eliergy regioil cenl,erecl arolllld l,lle al'gorl"11)l'eSOllit;li('O al:)oul, 3 e\: below Llie K-shell pliot, oiollizat, ion i,hreshold iri l,}ie K-sliellal:>soi'p{ioil specl,rtiin, ']'tlis is dlie Lo c,aplure, of \lie I( electron I;o a.1)olilid 4p orl,,ii.a.l.'J'll_:,ie is a. f_,liggesLioli iii 1,he Ar a+ dal.a ot' capl.ure of t,lle I'( elect,rori 1;obotlnd 51) ail_:l61.)sl,i_l,es also. ,cg'iinilill.'d_d,a,liave 1)eell o}TJl,ained irl, nla.iI.'),ell(!l'giC,.q for l,lle ot,]lor kllgert.ra.lisiLioiis respoiisiiJle for fillilig i,he illit, ia.11( V_'i(_'i-/liCyand exllibit, feA-it,lli't?s similar1,ot,llose stiO\Vli for l.]le Iq-l,,.,aI,u:_(:oirlci(Ieill, dltt.a. '.['tiese. pronouliced sllil'l,s iri clia.rgesl.a.i.ea.re liOl; evldelit, in specl.ra, not ol.)Lidlied ill coiliciderice.

'l._}le expeririie111_required aboul, eiglll, da.y,s.'oi l:l(;i.un Lime, illcluding fOlll' sliifl;s ofl.ii-nilig-illo{le opcrat.iori, and was perforliied ilt l)ect'llll)c'r, 1989, Oil _N_1_]7,_l)ea.rnlirieX-:2-1.,\. ()111' i/.1)l)_lra.i.us COliSiSl,ed of a Lirlie-of-t!iglil, Sl)OCl, l'Olnc, t,e,r tO detect, i-iI'gOli iorisand it. cvliil_lrical rnirror ailalyzer Lo selccl, l)a,rl, icll]ar Auger elccl, roiis. Data. werecollect.e_:i lising {,lie X-o,IA 1_131' COl_lll)Ut,<'r. 'l'tie eXp<'l'illlCIlt W&S l)repared ai, the Oakl/i<lge Nal.io,lal l,_:lborldory iii {it,]:JOl'&f_Ol'it?soccupied iJy l,]le Ulliversi.l,y of '{7'fJiill(:'ss('eaccclerai,or-1)asod a.loinic plib'sics groi.ll:>arid l,ra.llsporl, e(1 {o NSLS. ()lJl' gas-l)llase ex-t)el'iilielil: was isolated fi'oill ring \'aciiiliil })y a. })ervliiillli wiridow.

\Vr, l)rOlJOSeIo (:Olllillll(7 o×l)(;'rilllt:lllS very siilliiar 1,o l,]la.l, disci.lsse(] alJovt: tiSillggasool.is XfiJlOII. 'l'lie <.'xporil_leliia.l al)i)al'a.f011s will remain virl;ually iliit'llari_(.;(l. Iiisul:,seqlielil; e×i)oriiiit'rll, s>wo liope to provide diff'ert.'.litial I)l.illll)ing 1o perliiit, reirio\'alof lile })ery]]illlll v:iil(]o,,v arid access t,o l)]lOlOli c'llorgic,s lower l.}i;l{ {lie 3 keV wilidowcii\off. Tlli.s will l)erinil exl.ensioli of t.iiese exlloi'imeiil.s to the I, edge ot' l<r,)'l)lOli aridllie ]'_ edges of ll(,C)ll and ht:liulrl.

1. ;['. ek. (.',_lllsoll aiid Sl. O. Nrause, Pliys. Rev. 1:77, A16,55, 196,5.2. '1'. 'l))llunia, .ai. Yagisliita, II. Silil)al, a, "1'. l(oizumi, T. l_Ialsuo, K. ,_liillia, '1'.Mi.il,:ovan-ia, arid II. '].'awara, ,J. Ptlys. B: At. Xlol. l']lys. 20, 1,3]-L3(i, 1987.

--- :7..J. il. S<'ofit_]<.l,Al. l)ala iN'lit'I. ])al.a 'Pables 14, 121, 1974.•I. _kl. I|. Clten, B. (7'raso_nanrl, and II. _lai'k, Al,. 1)a(.a Nticl Da(a, '1?able.s 24, J21,1979.

5. T. A. Carlsoii alid C. \V. Nestor, Jr., Phys. Rev. A 8, 2887, 1973.

6. G, B. Arlnen, T. _{berg, K, R.. Karim, J. C. Levin, B. Cra.semann, G. S. Browli,M. H. C.hen, and G. E. Ice, Phys. Rev. Let\. <_4,182, 1985.7. ']". Mukoyan_a, ,Journal of (he Physical Society of Japan, Vol..55, No. 9, 3054,198(;.

=

319

AR,GON-ION CHARGE DISTRIBUTIONS

FOLLOWING,

NEAR- THRESHOLD PHOTOIONIZATION,

JON LEVIN

UT / ORNL

320

MOTIVATIONS,

B. CRASEMANN : INNER - SHELL THRESHOLDPHENOMENA

S. MANSON : EDGES V/ELL KNOWN GLOBALLY,NOT LOCALLY

G. WENDIN : AUGER PROCESSES,RELAXATION,SHAKE-UP FROM INNER HOLES

M. KRAUSE : AUGER SPECTROSCOPYON 2NDDECAYS- RELAXATIONCOINCIDENCE BETWEENX RAYSAND AUGER ELECTRONS

M. KIMURA : CHARGEANALYSIS OF PHOTOIONSCOINCIDENCE BETWEENEJECTED

PARTICLES (PHOTONS, IONS, e-)

321_

ION CHARGE DISTRIBUTIONS

EXPERIMENT:

Carlson & Krause (1960's) Many papers,,

Lightner et aL (1971) Phys. Rev.A 4Many papers

SR --> Hastings & Kostroun (1983) NIM 208

SR --> Tonuma et al. (!987) J. Phys.B 20

THEORY:

Carlson & Krause Many papers(Shakeoff)

Mukoyama (1985) Bull. Inst.chem. Res.,Kyoto U.

Mirakhmedov & (1988) J. Phys.BParilis (Relaxation)

THEORY MUST INCLUDE:

Radiative, Auger, Coster- Kronig Cross Sections

Shakeoff

Relaxation

Change in Auger Rates Due to Depletion of Outer Electrons

Closing of Some Channels

322

z

* Carlson & Krause, Phys. Rev. 137 (1965)

_ _ Mukoyama, Bull. Inst. Chem. Res., Kyoto U. (1985)

- * K vacancies produced by x-ray tubes, filters

_ Monte Carlo simulation

_- 323z

* Krause& Carlson,Phys.Rev.158(1967)

¢ Mukoyama,Bull. Inst.Chem.Res.,KyotoU. (1985)

* Kvacanciesusingtubes / filters

_=MonteCarlosimulation

324

From Mirakhmedov & Parilis, J. Phys. B _, 795 (1988)

• I

-+-4-+-]--_;. I I1

r-- Kr i_20_ ,, ....

I 1

Od

0

0

0.2I,,,,,,.

005 _ .... -

O0 _'

2 z. 6 8 10 _2 It.

Chorge of ion

I Krause & Carlson, Phys. Rev. 158 (!967)

Monte Carlo

Monte Carlo with relaxation

325

These q distributions average over ali processes

==> Not sensitive to details related to individual transitions

.'. Coincidence experiment with Auger electrons, using veryhighly monochromatized light

COLLABORATORS

C. Biedmann UT / ORNL

C. S.O. "

R. T. Short "

N. Kellor "

I. A. Seilin "

L. Liajeby MSI

D. Lindle NIST

- 326

_--

TA CFD CFD

TDC

L_,, PREAMP

'_ _-_ PDP 11/34

.----................. ,:"_ MCPFIELD-_t_ '------.......... : -

"SINGLES"APPARATUS

DRIFT

TOF SPECTROMETER

D__..,__ - - _ iONIZATIONt FIEL i DRI'I:T 1 c_BER

[1_ I GAS CELL- EXTRACT

FIELD=

"_97

Spectrometer can resolve isotopes of Xe

-3*2

TIME OF FLIGHT

"White" x radiation above ~ 3 keV at SSRL

L123 vacancies created

328

-

. Breinig, Chen, Ioe, Parente, Crasemann, Phys. Rev. A 2_22,520 (1980)

329

TIMING OEV218 ..... I I......... I" ii ii I.....

4+m

2.4 --Ar Excitedat

,-tp Resonance 3+

2o - Noncoincidence

XLJ

1.5 --

5+

1.2.-Lr)

O.8 -- ?+

1+ u t 6+o.4-- ,,,n2+ ,

17.01 2 3 4 5 g 7

TII'£OF FLI(;I-{I"[xlO=]

4_ TOF

330

ARGONMEANCHARGE

4.50 l f I ......I..... l .... _ _

331

__

CHARGEFRACTIONvs hv

m01 i i i ....... i l 't .... i ' i

I4O

3+ 4+d =

F-o 1+_30

5+i.-

z20 2+5cL _ 3+

10 4+ - 2+_4-,

5+14-

0-0.60-0,40-0.20 0.00 0.20 0.40 0.60 0.80 1.00

PHOTONFD,ERGYRELATIVETO 4P [xlO 2 ]

At the 4p resonance, -,,2.5 eV below Ar K ionization threshold, q distributionshifts abruptly to higher q.

332

HOW CAN AN Ar K VACANCYDECAY?

K - L23L23

K- L1L23

K - L23M23

K- LIL1

K - LIM

K - MM

RADIATIVELY

MOST IMPORTANT

_ 333

NOTATION:Ex: K-L2L,3

M5 3d5/2M4 3d312M3 3P3/2M2 3Pl/2M1 3Sl/2

L3 . .,"L 2P3/2'' 2 p 1/2L2 ,.,

L_ l 2Sl/2

K O lSl/2

Advantage of requiring Auger coincidence:

1) Ali initial vacancies are guaranteed to be in K shell.

2) First decay is specified.

334

cr_ _ rjZl-- • ZC:C:

C_ n"

335

WHATCHARGESTATESARE MOSTLIKELY

FOLLOWINGEACHK-AUGERDECAY?

K- L23 L23

L_L- MM Ar4+_L-MM

K-L L1 23

LL-MM Ar5+_L-LM

LL- MM

K-L M23 23 Ar3+

_L-MM

336

i

KL23L23, OEV

' '1 ........ I ....... I ' I ...... 1 '-'.....-i

H2.4 4+

K-L23L23 ' 3+ Arq+at 4p

2.0

5+

0.0

3 4 5 6 7 B g

TIMEOF FLI_ [×I0a)_=_

AFq+in coincidencewith K-L23L23 at 2600 eV with

ll_= 3203,8 eV (4p resonance)

337-

KL2_2_30EVI II I I II I ii ..... ii I i I I

4Q- K_L23M23 Arq+ 3+

at 4p

IQ- 4+

3 4 .'5 6 7 8 9TIME OF F'LIt_"IT[xlO 2 ]

Arq+ in coincidencewithK-L23M23at 2923 eV with

h_ = 3203,8eV (4p resonance)

338

KL IL23 OEV

5+

AFq+

I.O

4 +

Yo.8 K-LIL23

x_ at 4p

0.6

y

_o._

0.0

3 4 5 6 7 8 g

TIME[:IFFLIGHT[xlO2] '

AFq+ in coincidencewith K-'LIL23at 2575eV with

h_ = 3203,8 eV (4p resonance)

KL23L23 OEV

4+

2._ Arq+

K-L23L23 3+

2.O at 4p

,,.....

×1.5

For fixedaugerdecay,K-L23L23, now vary photonenergy,

340

KL23L23 -2EV

3+ Arq+

-2 eV 4+4O

5 +

, 3 4 5 6 7 8 g' Til'lE QF FLItg'iT [xI_ ]

K-L23L23coincidence-2 eV relativeto 4p

341

KL29L29 2EV

4+ Arq+1.6

+2 eV

0.03 4 S 5 7 8 g

TIMEOFFLIGHT[xIO2]

K-L23L23coincidence+2 eV relativeto 4p

342

KL23L23 5EVx._ I 1 i 1 ' -- I ..........

q+

1.2- +5 eV Arq+

IlO _'

Iii

X- I..,..i

0.8--

0.2

0.0

3 4 5 6 7 8 g

TIlE rF Fl_lg.-IT[x_O=]

K-L23L23 coincidence +5 eV relative to 4p-

343

KL29L23 I OEV2.B

4+Rfq+

2._ +i0 eV

0.03 4 5 6 7 B g

TIMEOF FLIGHT[xIO_]

K-L23L23 coincidence+i0 eV relative to 4p

344

,.0 KL23L29 50EV

LI+

+50 eV [email protected]

5 +

1.4

0.0

3 4 5 6 7 8 @

TIMEOF FLIGHT[xlO=]

K-L23L23coincidence+50 eV relativeto qp

" 345

2000 .... 1 ..... I ' "' I........ - I

oo 1500- K-L2_L23 4+

Z • AP +

O A Ar4+©

1000 - T AP +L'q 3+

<I( ionization

c_ 500- thresholdO

2:; 5+

-1o -5 0 5 l0

PHOTON ENERGY RELATIVE TO 4p (eV)

Ar3+'4+'5+ coincidentwith K-L23L23auger decay normalized

to constant pl3oton flux,

° 346

0-10 -5 () 5 1()

PHOTON ENER.GY,RELAT1VE TO 4p (eV)

Decompositionof Ar3+ coincidentwithK-L23L23augerdecayintocomponentsdueto excitationof K electron

intoboundnp levels,

=

347

RR@ON 5+14+ RRTIO

50%_

0.40

K-L23L23 coincidence

0.30-+ Ratio of Ar5+IAr4+ -

+LC)

0.20-

12%--_O.IO -

K ionizationthreshold

0.00 I_ I I I I I-I 0 l Z 3 4 5 6

PH_TCNE3_ERGYRELRTIYETO 4P [xl02]

Ar5+/Ar4+ r@tio depends strongly on In_

348'

WITH HARDER X-RAYS (APS?)

1) Do coincidence with less probable Auger lines(e.g.,K- L1 El).

2) Operate Auger-electron channel at high resolution.

3) Triple coincidence with photon, Auger electron, andphotoion.

4) Do spectroscopy of secondary, tertiary, Augerelectrons to study relaxation.

=

349--

Nuclear Bragg Diffractionof

Synchrotron X-Rays

' SSRL,,John Arthur

Dennis BrownGeorge BrownBill Lavender

Stan RubyL

APS,Ercan Alp

Gopal Shenoy

Allied-SignalDevlin Gualtieri

350

i

Nuclear Bragg Diffraction of Synchrotron X RaysL

In the last few years several groups have successfully carriedout experiments involving the excitation of nuclear resonances usingsynchrotron radiation. Ali the experiments so far have used 57Fe asthe resonant nucleus. The extremely narrow width of the 14.4 keVresonance in 57Fe makes these experiments very difficult at even thehighest-brightness synchrotron beam lines currently available, somuch effort Is being devoted toward improvements in equipment andtechniques. The general aim of this work is to use resonantscattering to produce high-flux beams of extremely monochromaticradiation, which can then be used as source beams for a variety ofexperiments.

This talk, however, will stress the kinds of physics questionsthat can be answered using broad-band sychrotron radiation toinduce resonant nuclear diffraction in perfect crystal samples.Experiments of this type are being carried out today, albeit withdifficulty, using present synchrotron sources. They will becometechnically easy when advanced sources such as the APS becomeavailable, and it is expected that nuclear Bragg diffraction willbecome a standard technique.

- 351--

A!

, next level 122 000 eVI_

3/2 _--

1/2.....~ 10.7 eV Firstexcitedstate

-1/2

-_2 , " i1• I

I

1i- " 14 412.5eV

|

] '!

-1/2 ii10.7 eV Groundstate

1/2

57Fe nuclear excitations

352

Current areas of development

I. Resonant filters for producing intense, highly-monochromaticbeams

_Using crystal and multilayer diffractionTischler, ORNL (NSLS, CHESS)Kikuta, Tokyo (AR-KEK)

_Using grazing-incidence scatteringGerdau, Hamburg (DESY)

• _ Using transmissionRuby, SSRL (PEP)

II. Physics of resonant diffraction from perfect crystals

Gerdau, Hamburg (DESY)_ van BQrck,Munich_- Smirnov, Moscow

Siddons, BNL (CHESS, HSLS)_ Hastings, BNL

Brown, SSRL (PEP)Arthur, SSRLRuby, SSRL

= 353J

_

_

Applications of resonant diffraction from crystals

I. Materials science probe

Very accurate measurements of hyperfine fields in magneticcrystals

II. Showcase for quantum interference phenomena

Interference between resonance levelsControl of quantization axis, polarizationInterference between states with identical energy eigenvalues

III. Crystallography in a new dimension --interference effects onenergy and time dependence

SpeedupDeviation-angle-dependent energy shifts

354

PEP as a source for resonant nuclear diffractionexperiments

A number of factors combine to make the PEP storage ring atSSRL the premier source for experiments requiring extremebrightness at 14 keV. The high electron energy and large ringdiameter make the electron beam emittance small. The 26-periodpermanent-magnet undulators at beam lines 1B and 5B have kparameters close to unity when the first harmonic is adjusted to14.4 keV. The X-ray beam produced by one of these undulators has adivergence which is only slightly greater than the angularacceptance of a typical diffracting perfect crystal.

355

=

• _.I /

PEP Characteristics

Ring circumference 2200 m

Electron energy 13.5 GeV

Source size 2 mm x 0.2 mm

Electron divergence 50 x 40 14rad

Insertion device 26 period undulator

Photon emmis$iQn .7.5 LLrad,.divergence

(SPEAR 170 urad)

Source - sample distance 56 m

Typical beam spot size 2 x 0.5 mm

Flux @ 14.4 keV 1012 S-1

570o PEP undulator

Flux into 0.01 sr(photons.sec-1. 106 104

10-8eV BW)

Brightness(photons.sec-1. 103 106

mm-2.mrad'2.10-8eV BW)

358

Resonant Nuclear Diffraction Geometry

YIG(002) Si (111)monochromai:orScintillator

Electronics

359

I

YIG

Yttrium iron garnet has a rather complicated crystal unit ceThe (002) reflection is forbidden for scattering from atomicelectrons, lt is also forbidden for nuclear scattering from most ofthe Fe nuclei. However, two groups of Fe nuclei, which haveopposing phases for scattering, can be distinguished from each otherbecause they see local electric field gradients which point indifferent directions. By aligning the internal magnetic field parallelto the EFG of one group and perpendicular to that of the other, theelectric quadrupole shifts of the nuclear resonance energies for thegroups will differ slightly. Thus the scattering from these Fe nucleidoes not cancel exactly. The scattered amplitudes are initially outof phase, and cancel at t=0. However, as time passes the slightdifference in energy brings the two groups into phase and thescattered intensity rises. The period of this "slow beat" is about130 ns.

360

YIG Crystal, structure

cubic unit cell, a = 12.386 A

24 yttrium atoms

96 oxygen atoms

40 iron atoms in several inequivalent sites

(a sites) 16 Fe atoms surrounded by oxygen ,,

octahedra

4 groups of 4, with EFG along (111)directions

(d sites) 24 Fe atoms surrounded by oxygentetrahedra

3 groups of 8, with EFG along (100)directions

1

-- TN = 550 K, (a) and (d) sites ferromagnetic but opposed toeach other

361

dl sites

d2 sites

o • ,! ! d3 sites

i

362

Magnetic Energy Splitting

_-" 4 - ]

t i tLHC RRC . LHC RHC I

t

Magnetic + Electric Quadrupole Splitting

_ 8.35mm/s ,_.._, i'-" 6.58 mm/s _ (100)group

0.66 mm/s m 7.02 mm/s __ "_I I !

_- (010)7.90 mm/s i group_

m

-- 363

2000 ,, ,, _,, .... : ....

1500 T = 295 Kr"

t,t -' " H - 368-__21<(3

_ 1000 quad,shN.- -0,85:_,,02mmls

850O

0 50 100 150 200 250 [_Time (ns)

240 , ,. .

|

200 , --,

_. . T_ 150K

'_ 160 F H TlkG

_'_m==120 ' '" " tt'v!li _ quld, shift -0,53_-K),03 mm/s8 80 . ,. _,4 .4

40 _ -__

0 ......., i0 50 100 150 200 250

Time (ns)

Time distribution of the diffracted intensity from the YIG(0 0 10)

crystal planes. This reflection has the same symmetry as the (002)reflection. At room temperature the internal magnetic field is notsaturated, it increases as the temperature is reduced. Highlyaccurate determination of the hyperfine fields is possible. Note thatthe information is distributed evenly throughout the data, and thatthe background is negligible.

364

1000 --,---_ .-, • ; , , .... v , ' , ,

800 - magnet_ field parallel _

'-'=E : _ to scattering plane

o 600 _r-_ iE= 400- ,O

° ;200

O_ :

0 50 100 150 200 250

Time (ns)

1200---, , , , , _ . _ , ....... , ......i

magnetic field perpendicular N

E

'_ 800 - . to scattering plane0 ¢ .;

o 400 - ; _ t _o -it li ,

0 ' ' ',. I .... J T ,-,',_",_,.,,___-=-_-- .... 1

0 50 100 150 2.00 250

Time (ns)

Changing the direction of the magnetic field in the sample relativeto the photon polarization direction changes the polarizationselection rules for the different hyperfine levels, and therefore

changes the nature of the interference pattern. The beat pattern in(b) is dominated by interference between two levels which inconfiguration (a) have differing polarization and therefore do notinterfere.

36.5

2000 "-'_ ' ' 'r ' _ ' ', ....., '

YIG (002),@

1500 ii _

E0

"---_1000 .- _t!:_ _ ."/'_l "'"",

° ii'5O0 ' ,,"

//

_ J J I , I I J I .! .| ..... "''T'_- "0 50 1O0 150 200 250

Time (ns)

A prominent effect of constructive interference on the energy andtime aspects of the resonant scattering process is the speedupphenomenon. The multitude of coherently-excited nuclei in thecrystal, scattering in phase at the Bragg angle, radiate power morerapidly than a similar collection excited incoherently. There is acomplementary increase in the bandwidth of the resonance. Thegreen curve was calculated using the standard 98 ns half-life forthe 57Fe excitation. The calculation neglects the fast beats due to

. the magnetic splitting of the hyperfine levels, but includes the slowbeat due to the quadrupole splitting. The data (and the dynamicaldiffraction calculation) show a much faster decay.

366

Deviation-angle-dependent energy shifts

The analysis of diffraction from a perfect crystal must includedynamical, or multiple-scattering effects. One of these effects is aslight shift in the effective resonance energy for the collection ofnuclei in the crystal, which varies with the deviation of the incidentradiation from th; Bragg angle. A deviation angle introduces slight,phase errors into the scattering process. For waves which aremultiply-scattered, these errors accumulate. In resonantdiffraction, waves which are multiply-scattered tend to leave thecrystal later in time than those that are scatterd fewer times. Thusthere is a correlation between arrival time at the detector and phaseerror introduced by the deviation angle. A phase shift that isproportional to time is a frequency shift.

The angle-dependent energy shifts are very small. They are,_ visible in the YIG data due to the particular details of the YIG(002)

diffraction condition. When the internal magnetic field is alignednearly parallel to the .incident radiation, some of the hyperfinetransitions are excited only by left-circular light while others areexcited only by right-circular light. The sychrotron beam is linearlypolarized, giving equal amounts of LHC and RHC light. Thus thediffracted time distribution consists of a beat pattern due to LHC

• light lying on top of a beat pattern due to RHC light. The angle-dependent shifts affect ali of the hyperfine levels, in a manner suchthat a shift which causes the LHC beat period to decrease will causethe RHC beat period to increase, and vice versa. A change in the

: deviation angle causes the LHC and RHO beat patterns to shiftrelative to each other. (The quadrupole interaction also shifts theRHC and LHC patterns with respect to each other, but this effect isindependent of deviation angle.) Even though the angle-dependentshifts are very small, it is easy to observe the shift of the RHC beatpattern relative to the LHC beat pattern.

_- 367

- _ .... _, _p, ,_Ir,...... ,

¢'

,_'-lr I1el',

© ,.,--) ..... ,_ .... _ ........ "3. -,::) .....0 ...... @ _,-_,-_"_ i;' ' - __-,-:11-- r

'L) _'_ :_ ._) .... ) - ,L)........ _L_- ;_)

The deviation-angle-dependent frequency shift

A phase error that increases with time is a frequency shift

368 i-

l;l=_

II ,rr' ' 111 ' " .... lii 'r'

C.,_)_.,/ " • . • ! ' • • • I " ' ' ' • I ' I' _ • _ I ' ' ' '""' •

600c _ b4-)= -33 u"ad

O

--- 400 _' _[ ""C _j "O qO _ ,r.

200 ,': ",

0 50 100 150 200 250

Time (ns)

2CDO . • ' • • ' • , • • . • v . • . ' . v ''_' . • . , . "T'_s'-=s=--

.i+.

• P,I

1500 / '4, P "

o . , ' % bU=-5urad

-----1COO , ._•,-.., t" .r"- "'

= t' _0 ° •

o ,:500 ' ' +'

:' Jl, ._

• ,r

00 50 100 150 200 !50

Time (ns)

500 ,' ii", ,"v I ' ' ' ' I , v _ , i "i I', v I ' ' V v

400r'- _ " '

E "; "• o 300 - . _ _0= +31 urad

t_ Ii"

200 . , ,. ,

. • II=,

0 . , .... __3i,.-'., ..... _le_0 50 1O0 150 200 .;250

-_ Time (ns)

369

Revealing Inner Shell Dynamics with Inelastic X-Ray Scattering

Carl Franc.k, Lab(_ratory of Atomic and Solid Sta, te Physics and Materials Sci(:,nc(, C_,llt(,r,

C_rn(ql University, Ithaca, NY, 14853

(),lc, of the many (_l_l_ortmlitics provid_:d by the Advanced Phc_ton S(mrc(, (APS)is

t.(_cxt(,l_d rh(., study of intra-at()mic dynamics. As a means of t.(,sting (lynan_ic r('sp(_lls_',

inelastic x-ray scattering is imrt.icularly promising since it allows us to ind('l_(mdr'ntly wiry

the 1)cri(_(1 of til(, (,xciting fi(,ld in l_(.)th space and time. As an (,xamI)l(" of this tyl)(' ()f

wr)rk, w(, 1)r(,s(,nt. _xi)(,rim('nt.s 1)('rformcd at ihe Cornell High Energy Syn('hr()tr()ll S(mr('(,

(CIIES S ) lal)or_Lt (,ry, a 1)r()l.oI yl)C for i.hc A PS. This was iml(,r sholl in(dast.ic s,,'at t(,l'ing witll

a twist: in ord(."r t()(:'xl)l()rc a m!'w dist.anc(:_ scale an x-ra:, thu)res('(ulc(_ trigger was (,_nl)l()y(,(1.

Asi(tc fin the atol_lic insight gainc(1, lhc experiment taught us the imt)(:)rt;alc(' of rh(, tinl( _

stru('tur(, ()f rh(? ,,..;yn('hr()tl:Oll ])oa.ill for coim, id(mcc cxi)oriments whi('h ar(_ (l()milmt(,(l l_y

_tc('id(:._t al cv(,nt s

This work was performed in collaboration with Vincent hlarchetti (1)res('ntly ai: N,,-

('l_,ar Sci(,n('(_ _nd Engineering Program, Cornell Univ.) \'ital assistance was provid(:d 1)y

CHESS scientists, staff, and us¢_rs: especially D. Bilderback, hl. Be(lzyk. L. Bern:an, B.

Batt.(,rman. II. Al)tuna, and W. Bassctt. Support w_Ls1)rovidc.'d by the Naiiolml S('i(,n('(_

Fo, mdati(m through rh,, 5I.ttcrials Science C(mtcr at Cornell a.nd the Low T(::nlI)(!_ratur(:_

Physics Program grant DLlr/-8611350.

37o o

.

I would like to thank til(: organizers of til(. conference for the opl_ort,ulity t.o l_ring

to your attention two types of CXl_erimcntal techniques which I thii_k hay(: imi)ortant,

possibilities at the .Advanced Photon Source. The first is inelastic x-ray s,:att(?rin_;. As

Professor \_'(:ndn: pointed out earlier, lids is a versatile prol)e for :Lt.o:nic dynamics in that it

operates over a variety of lellgt.h and tim(., scales. Tll(, secoild tcchniqll(-: is tlm nl(_asm.',_l,l_lit.

of multiplc' decay pro d,(cts following an x-ray / target int('raction. I will also exl>lain wily

when one is attempting to p(:rtl)rm coincidence detection in order to study a w(:ak proc(,ss

with a high incident flux there C_I.1Il)e imI>ortant accidental coincidences which must 1)(,

1_Sclll_(:.oltrovercome. The context in which I will make my presentation is to ( e" "- _ syn(!hrotr_)li

experiment in this field: an inelastic x-ray scattering study of the ex(,itations of the COl)p(,r

I(-shell whi(,h used a. fluorescence trigger. By l_resenting this experiment I will not ()111_'

try to convince you of what I think can be done at the APS but als() share sc)me (_f rh(,.

lessons we learned in the hope that they might assist such end(-'avors in the fulure.

hl), outline is as follows: First I will give the motivation for studying inelast, ic x-r_y

scatt(,ring, and the need fc)r measuring this process in coincidence with x-ray flllor('sc(,1|,'( ,,

This reqltirement arises because of the possible spectroscopic overlap ¢,[ tlm signals fr()1_)

(-,inner and outer shells. I will then give the d(;,sign of the experiment performed at _HESS.

Next, I will present observations and results in comi)arison with work in this fi(,ld using

radioactive sources. I will thc:n describe the most impoa't.::nt 1)hony signals il.t tllis work.

The tirst type is something I have ah,..a(ly alluded to' chance coincidr, nces. Th(_ second

type arc avoidable coincidel-lCCS due to l_h()tons passing directly 1)etwe(m dr_te(:t()rs. Finally.

I will summarize and give sonic idc.'as for t',ti,,re activity at the Advanc(:(1 Phot, on So,,,'('_,.

\\'hat is inelastic x-ray scattering? As Fig. la indicates we are interested in I)rocessr:s

which involve a single photon incident. (ma target with a precise energy E,,, and mom(,nt_n)

1_.,,. Subsequent to the interaction a single scattel"cd 1)hoton (:m(:rg('s with (:n(,rgy E_,._,_,

and mom(,ntuni l-;_c_,tt at a scatt(:ring angl(:. 0. If the incid(?nt en(:rgy is suffici(,ntly high

compared to the shift in energy b(.t'c>re an(l after the, collision, then one ('a_ b(' in (h(, Born

= 37i--

approximation and think about the scattering as the measurement of the dynamic structure

factor of the target, S. S has two independent variables: tile energy transfer, E, which

is the difference between incident and outgoing energy, and th.e momentum tl'ansf('r, q_

which is the di_'crox_.c_; between incident and outgoing momentum. One can imagine (Fig., ,'/ ,

/

lh) that the _.:,__.__s}_.c.scattering,. process consists of the absorption of an electromagnetic

disturbance which has an energy-momentum relationship wlficlt is unattainable with an

orclinary photon. A third way of describing the process is that we are studying the response

0f the target to an electric field which oscillates in space with a wavelength I)roportional

to 1/q and in t.ilrt(-'with a frequency pl'Ol)ortional to E.

Iu order to develop our intuition as to what it means to measure the dynamic structure

for an atomic system let us first cc)nsider the 1)roblem of a target which is nothing but a

stationary free electron, tire problem first understood by Compton. In Fig. 2 I sltow

the dynaxnic structure factor at a fixed nlomentum transfer. The variable here is the

energy transfer (E). One sees a very simple spectrum' a peak at an energy transfer

of q_/(2rn,), where m, is the electron mass. 1 The peak width is proportional to q times

the characteristic momentum si)read of the target divided by m. 1 Since for the case

at hand, the momentum spread is zero, we have a delta flmction peak. Now consider

a bound electron as our target, sl>ecifying the wavefunction size to be (t. First let us

consider two extremes of momentum transfer. At very high momentum transfer, that is to

say q nmch greater than 1/a (the characteristic target momentum spread), the dynamic

structure factor still has a peak at q2/(21n.). However, as shown in Fig. 3, the energy

st>read ]ms broadened because 1/a is nonzero. Such;_m expe:riment is famihar to us as

the measurement of target's initial nlOnwntum distribution w;th Compt, on scattering, lt

does not give us any db:namical int'c)rmation. It does not reveal new information about

transitions to excited states in the target, but instead it, measures the initial state of

','he target. In the opposite limit of extremely low momentum transfer, i.e. q much less

than 1/_l, the dynamic structure ftLctor h_Ls a more interesting spectrum. As shown in

= 372

Fig. 4, we have a threshold at the binding energy of our target electron whictl is given

by Eo _ (a-1)2/(2m). At higher energy tr_nsi'ers, we haw_ transitions to bo,md states

and a broad continuum of tra.nsitions t.o unll)ound states. At t,his point, I would like to

remark that throughout our discussion, the incident 1)hoton energy is nowhere ,war an

absorption resonance. Tlms, we are doing non-resonant inelastic scattering, in c()ntrast

to the resonant process discussed by Dr. Cov,,an. Non-resonant inelastic scattering at

small molnentum transfer gives us the same dynamic infornmtion as a l)hot<:)absorl)tion

sI)ectrum. This is because the transition operator for non-resonant inelastic scattering in

the Born apl)roximation is given by exl_(iq-'.r-') _ 1 + iq-'.'F-q'2r2/2 where r-*= target el<.'ctr<)n

position. We see that for small momentum transfers, the second term is what matters (the

first term gives no contribution to the rat<:). It is the electric dipole operator, the same as

in 1)hotoabsorption.

The 1)urpose of our work was to explore im_cr shell dynam.ic stru(:tur(', in the interme-

diate momentum transfer regimc', that is to say q on the order of 1/a,. ttere the spectrum

looks unfamiliar (Fig. 5) because it, includes electric dipole forbi(lden transitions. We

were attractc'd to this regime 1oy the rei)ol't _ of Namikawa and Hosoya of new spe(:tral f('a-

tures involving K electrons at intermediate momentum transfer in COl)per and iron targets.

There is an inherent difficulty in maldng such measurements because of spectral ov(,rlal)

between the scattering from the electrons of interest and the outer shell electrons. See Fig.

6. This comes about as follov,'s' The conditi(m of q is eqmd to 1/a implies that peak ('ilergy

due tc) outer shell scattering has t.he sanle v_due as the thresh(:)ld energy fin' the spe('trmn

of the inner shell. The question for us is h()w to extract the dynamic structure of the K

:lectIon excitations from the composite sp(:ctrum. Tlm solution was devised long ago (see

for example Ilef. [3]). The trick is to watcJi for a K-shell fluorescence photon as a tag of

which electrons are involved iii the in(,lasli(' scattering event. As shown in Fig. 7, th_, inci-

dent. high energy plmt on excites a 1,2-shell electron. Some ft'action of the tirne a very quick

refilling of the hole occurs with the (,mission of _ ehar;_cteristic 1,2fluores('ence. 4 Sr), tlm

373

experiment consists of l(_oking for inel;tsl.tc scat t_,ring i1_coincidence with K flmn'escence.

Nov,' I will describe the experiment that we did along these lines at the Cornell ttigh

Energy Synchrotrcn'l Source. (.)11r inlor(_st was in t.he COl)per I( shell, tlere _l is Oll the order

of 0.016 ._. Therefore we. needed mOlncllt.nln transfer around 60 ._-I in order to be in the

intermediate regime. Since we wanted a c(mvenicnt scattering angle of _90 ° we chose an

incidc, nt (,nergy of 70 keV. I should pot,tr out l h_tt tile scattering angle does not completely

determine the momentum transfer. At a iixcd scattering angle, the mornentlun transfer

depends t.o some extent on tile energy trallsfcr. N(,verthcless l:)yscanning the energy loss as

well as the scattering angle one is al)le t.o get the equivalent illformation to having energy

and moment, unl transfer as ortl_mgonal cont, rol varial_l('s iii the experiment.

Thc'. design of our experiment was as f(_llows.:' Tile l_eam was generated in tit(, Ct!tESS

six l?ole wiggler t'ed by an ,.w,5 GeV" electr(m 1)earn. A double cryst.al monochroma.tor was

used in second order to reach the reqllired energy. A copper filter suppressed the. 35 keV

fundamental. The layout of the rest. of the cxperilnent is shown in Fig. 8. In order not

to overload our photon detectors, the target was a thin (typically 8 micron) solid copper

fl._il. _Iost of the im'ident l)eam passed througil t.he target and into a ionization chamber,

which served as a beam monitor. An energy s(-,nsitive detector was oriented so as to give

a vertical scattering plt-me. In order to lnillimize tile amount of scattering into the second

solid state detr,ctor, which detected the ttuorescence, we located it in a horizontal plane

looking into the primary direction of polarization of the incident photons. Fig. 9 gives a

rol|gh layout of the electronics. The idea was to measure the spectrum in /.he scattered

1)hoton detector when a photon al)l)eared in thr, low energy fluorescence photon detector

in thr.' correct energy range. Our timing was accoml)lished with a f_Lst coincidence chain

and tile SlmCtroscol)y through slow coincidence.

I will now present our observations. Fig. 10 shows '1 the spectrum of scattered photon

energy in coincidence with K fluorcscem:e at a. fixed scattering angle (90 °). Tile ol)serva-

lions are tile data points. The tlmol'y, to be discussed l_Lter, is given 1)5, the curve. The

37/4

inddent energy (70 keV) is indicated. The (lat_ has been normalize'd, in a mann('r to be

discussed be.low, to give the triple differential cross section with respect to scattered 1)hoton

energy and the solid angles for detection of fluorescence an(l scattered 1)hotons. In order

to know the energy energy transfer ones simply subtracts the incident from the scattered

energy. Iii order, to improve the statistics, the spectra were 1)inned into 2 keV wide chan-

nels. The primmy features in the sl)ectrmn are 1) the shar I) rise at an energy transfer ()f

9 keV, which, as expected, is around the I_ binding energy, and 2) the subsequent broad

continuum of excitations for higher energy transfc'rs.

Let us first cheek to see if this is really inelastic scattering. To do that we shifted the

incident energy from 70 down to 62 keV and as Fig. 11 shows that we got a eorresp(mding

shift in the scattered spectrum. No change in amplitude is seen because this is nolt-resonant

inelastic sc_ttering.

Next we would like to check to see whether the excitation-dcc_:_y 1)rocess ()(:cnrs in the

rnanner in which we had indicated earlier, i,e. through two separate stages. In or(h,r to find

this out we reversed the roles of our two detectors and measured a dec, ay photon spectrmn

: from the low energy detector in coincidence with the detection of a scattered 1)hot(m in

- the energy range that we had established as c<)rresponding to inelastic scattering. We used

= the same electronic plan as before (Fig. 9), except that the signals from the scatter(,d and

fluorescence photon detectors were exchange(l. The data points in Fig. 12 are the result ()f

_ this experiment. They display the familiar I(a (_, 8.0 keV) and I(/_ (,-_ 8.8 keV) emissi(m

lines. For comparison, we ol)tained the decay spectrum produced by 1)hotoabsorl)tion (also_

__ shown in Fig. 12), normalized to agree with the inelastic scatterillg-1)roduced spectruin.

The two spectra do in fact agree, SUl)porting our hyI)othesis that the (lecay process is

independent of the ,neans of excitation.

. We are now iii a position t,o sweel) monul,nt, um transfer ov(?r ;1,wi(le range by (:hanging--

- the scattering angle. 6 Fig. 13 gives the results. \Ve have chang(,d momentum transfer

corresI)onding to (llstle scattering (q0) by a factor of two in the interme(liat(_ momentum--

375--

--

_,,n.,'L_' , ' ,_,

transfer regime. The spectrunl rem_tins pretty much the same. The data collection tim(,

in this eXl)erilnent was trl:)out 6 hcmrs for ea¢'l, ttllgle,

lt is interesting to con-lllare Ol11' synchrotr(m eXl)erilnents at interm(:,diat._: in(nnentum

transfer with those performed with radioactive .,-;ottr('(:.!sboth bcRn'e and afWr omr wc_rk, Tlw

isotope used was Am _41. It, has an _'nlissirm at 59.6 keV, In the eXl_erim_,nt of Namikawa

attd Itosoya, _ which inspired ollr work, a 0.1 Cm'ie source was us_-'d to ol)tain tlw scattered

photon Slwctrum in coincidence with I,_-fluorc.'sc(._nCe shown in Fig. 14 for ('Opl)('r and iron.

'For ('opl)er , 1400 hours of data. was used to gcr this result at a single scattering a.nglc.

hIany more Sl)Corral features arc.: indicated than in our work, Namikawa and H()soya _

and hIamlin(:n "r pointed out that false coincid(:nccs nec dod to bc consid(:,red. Manninen,

Hamalainen, and Graeff( -s have recently mad(' a scc'()nd s_,t of radioa(',/,iv(!, sour('(._ mcasm'_;-

ments, this time with a 0,9 Curie source. Fig. 15 shows their measurements als() at a

single scattering angle over 67 hours for both copper and zirconium. Their spectra are

in good qualitative agreement with ours. Notice that they have superior statistics and

scattered energy resolution compared to our work. This was facilitated by their use of

a large soilium iodide detect(_r as a fttioresc(:l_.ee detector. While degrading ttuoreseence

resolution, the increase in solid angle enhanced their counting rate. Our results were ob-

tained iii considerably shorter time than (,itlwr radioactive source measurement. We also

covered several, not just one, scattering angles. But, as I will explain below, radioactive

source measurements have an important advantage over pl_lsed source cxperinmnts, i.e. at

CHESS or the APS, with respect to the rate of accid('ntals.

One of the important aspects of our work not present in the cited ra(lioactiv.o source

work has been to give al)solute norrnaliz_Lt.i(m to the spectra. This has been of vital

assistance in interpretation, especially for background effects. In order to normalize the

scatt(_ring Sl)(,clr_t we measured the fluor_,.s(:(,nce rate due to 1)hotoabsorl)tion to get the

incid_,nt tlux. With knowledge of the d(.,.lc',ctor cfiici_:ncy and solM angle subtended we

got a1_ al)solut__ uncertainty of -t-15_2f)for th_ data (_f Fig. 10. In earlier work (Figs. 11

376

and 13) t,h(; absolut, e mlcert, ainty ,,v_Ls-_t=..1()¢S,,Nc)rmalizat.ic_n also st,r¢,ngtll_,llS t,(:,st,s ¢)t'()ur

understanding of dynamic structur(' at int c,rlllc,diatc,,momcntmn tralisf('rs. Th(, s()lid lim_s

in Figs. 10, ll, a.:l,d 13 show tlt(? rc'slllt, c,f'a olt¢,-(,l(,ct:'c,n th(,(,ry l_as(,d ()na h)c.al (Slat(,()

al)prco_ina.tiozttoHartree-loci:th('()ry.\V(,find good agr_?(,m(:nl..Ii1l)_,rli(,::lar,wc rf()

lH)t,findrh(:l)r()adl)(:,al:intlt('('():it.ilil::::l:('iI(:(ll_yNa:nikawaanrlII:,s(,y,L._ Th('-,v()rl:,,I:

Mannixi(uietal.s s,.xl)portsthiscon('h,._i<,1:.

I would now liketo Cxl)l:linhow in or<ftu'to ()l)t,ainour :.(,suitsw_?<(,'(,ream<'tw<_

importantCXl)crintontaldiflic:11t.i,:,s.Thr?'_L:'(,b()th(.'Xaml)h"s()I'l)!iony('()in('i(l(,,l(:('s.

The first kind of phony c(,im'iden,::(_s at',, chance coincidences. I((,call thai, w(: at'(,

detecting procosses in wllich a 1)_ir of 1)liot:ms (,mer_e fr(:):n th(_ ta.rg(it si:m:lta:w<?:_sly,

to within our resolution in time. \V¢, ar(: (_nly i:ltcrested in collisions inv(_lving a singl(:

incidc,nt x-ray striking a single atom, but ;v(' might d:'t,(,ct, a pair of ph()t(_ns 1)ro(lu('ed at,

s(,parat, o at()ms struck l)y a pair ()f i:,cid('nt x-rays. (See Fig, 16) F()r (',Xaml)l¢:, when ()Ii('

sees _t pair of l:)l_otons emerging witll a high and a low energy, d()(,s tlm ('v(:nt indi(,at('

inelas/,ic scattering of a siliglc in('i(h.,nt, photon by the K-shell with tlw ('missi()n (>f ht-

fiuorescencc or does it indicate that two high cn('rgy photons interacted with separat(;

at0::,.,, one performing inelastic scat tering fr(.)m tlle outer shell, rh(" oth(:,r 1)(.'ingabsorl)ed

by tile I(-slM1 and giving IC,.-fluor(,scence?

= Our singles rate (:'atc of detection wi{hout r(,gard to c()inciden(:e) was k('l)t low, al)()_t,

4 x 10:_ Hz, in ord(;r to giv(:, good (:,n(_'rgyr('s()l_:ti(.)n. One might th¢:,_:ask, why is t,h(,r<_

' Sa problem with accidental events at s_:ch a low rate? The l)rol)lem is that CHES, , as

wiU be the case with the APS has an ('xtr(:::lMy low duty cyclr._,.At CIIESS, rh(:'1)hot(-ms

come in bursts of _ 0.2 ns(xi. (h:rati()n whi<'h arc on for only 0.05% of the' tim(' (that is

= t() say al)l.)r()ximat(:ly (:.,v¢,ry(/.4 /ts('c.). T]::' d|:rati()n ()f r",:__h'b:_rst was not, r(,s()lva])lo i_l

tim(: by o:n' (:l¢,ctronics. Bath('(, f()r rh(: s()::rc(, intensity as a f:mction of tim(:, w(' hay('

: the _(l_fi','al('nt (.)fa string of d(,lta t':nicti()_s. B(,cause <)frho c(:m-_I:)r_ssionin tim(:,, the' raw

_ ofaccid(:,ntalcoincid(:ncesis(::nhan('r,d.In l)r_('tic('",v(:tyl:)icalJy!roda tot.alc(_in('i(lon<'('

=

3YY

rate over the entire sI)ectrunl of inter(_st of 2 Iiz, with (rely 5% of this r(,i)rcsonting true

coinciden'ce, o.vent,s!

tt()wever, tile l',tte for Imi'i(..h_lltM r._.)ili('i(h'nc(' ('Hll l)(' easily m0asltr('(1, The i(l(,a is t()

run a cx)ntrol exi-)(,riln(mt witl_ tl.:' t,w()det(,('t()rs s(,1,araird ill time, \Ve (lid this 1)3" usillg

signals from lh0 (l¢!tct:i()rs c()rrc, sI_c)n(lillg t()(litt'(,r(,nt pllls(_,s fr(mt C.ttESS. hi fact, w(, Sl)tilt

equal amounts of time with the dot(,ci.ors (,li the s_lnie 1)ltlse alitl mlccr"ssive pulses, We

switched l_(:tw(:,un tl.ios(: two modes ov(,ry s(,-,,.'ral s(_c()n(ls. Tyl)i(',al results are sh()wn.itt Fig.

17. It, is imp(1)ssil:)h, to s(;e the diff(:,r('l_c(, 1)t,tw(:(,tl lh(, tw()tyl)eS ()f rave' Sl_(-,ctl'a 1)3' (,ye. Th(,

slight diif(_r('n('(,, sl)(i'('trlllll is the sigli*tl in wlli('ll We are inl(',r('stc(l. N()tic(', that th_' gr(,at('st

uncert_dnty in the difference spectrllln oc('ltrs, ,ts expec.te(l, at an energy c()rresp(mding to

a peak i:t the singh,s spet't.runl (_lls()i:,li('at(,(l l.)y til(:',short horiz()nt, al lmrs iii Figs. 11 and

; :3).

tIow (lc)accidental coincidences c(.)ntril_,tt(., t,() tit(, design of sm'lt (,Xl)erinients'._ We can

ask the question: Wha.t is the irnl)()l't.anc(, of tl,:_ intensity of the soltrce, all other expel

imental.c(mditions (particularly the time st, rllctllr(.,) b(_ing equal ? The crucial 1)a, ralile|(;r

(A) is the rate of accidentals divided l)y tlm tmu: c(:,incidcnce rate. For us, A Val'icd between

about 3 and 30 over different parts of th(, sp(x'trulll. Fig. 18 shows '5 how we expect the,

noise to signal ratio to vary as a fimction of intensity and A. Note that we have norm,diz(.;d

the plots for tilt{in'ehf A to agree at _t reference ilttensity. "Wt, see that in ota.' work, there

would have ])eelt zt negligible improvement in the noise Lo signed ratio if the intensity of

tile beam llad been increased ])y a factor of 1(1.

A second type of phony siglial that we h_t(l t.() ()v(_rc(mic is due. to ph()t_:,ns moving

l)otw(;cn (h:_t(:(:t()rs so as t() Croat(: "crosstalk" coincidences, In (n'(ler to gain an aI)i)reci-

ati,)n ()t' the potential for such l)ackgr(,_n(ls, Fig, 19 shc)ws the singh,s Sl)ect, ra re(:()rd(_(1 l,y

thr:, scatt(,rc,(l 1)l_()t(m dot(,('tor wil..ll tll(' targ(,t in ml(l out. It sh(m's float th('ro at(' aI)l)re-

cia]_l(_ l)acl_'gr(:)_md ev(:nts. Au ii. turns ()_t, t lwl'(.' is c(msideral)!e suI)l)r(;ssi()n ()f 1)a('kgromM

(:vents whext we tm:n t()lh(', (:(.,in('i(h,n('c (,v(mt.s. Nevertheless, it was 1)r(,cis(,ly the l)rob-

378

_1_ , , ,_r , _ , ,,,_ _1_, ,,,,,pi, _1[ ,

lem of background events due to detector cr()sst, ulk t,hut, w_s Cml)lmsized by N_uulkawu,

Hosoy:L, _ alld Munnineu; us u sourc<., of 1)hcnly spectrtll i'eat,ures in the originul w()rk. A

Wpic.M cross:,alk eveiIt:, is iudh:_t,(,d iu Fig, '20: a siugle 1)hotou sc_tt, c'rs iu flu, t.argc't,

goes into the fiuoresceuce detector, dc,posits c'u:wgy via Compton scn.t, teriug, and th_: finM

SC'ratt,,,.'.redphoton (..sc,.l"":)cs"t(.) t,he sc('on(l ([c,t,ectol.'.

Our npl.n'o',.l,cl,. t.o this prol)leln wns to illst, M1 _lppropriate shiddiug, _md then 1)m'forul

control experiments to test its effic:_('y. Fig. 90 shows the ltlyout for u contr:)l (,xporinlm_t.

First,, with lc:_d (B in Fig. 20), w(' 1,1ockc.'d lhc (lir(,ct, view of _he target 1)y the sc:_tl.(,r(,d

l_hoton det.(;('t,or. \\re then me_ts:u'ed the tru(.' coin('id(,uce Sl)C'ctruni using t.he sul)t, ru('t,i(m

method described enrlier, \Ve got the "dc, tect.()r blocl:.ed" spectrun: shown iii Fig. 2lb. \Vc

set.' thut t.h(:r(: w_ts no significtmt Cl'OSSt.nll_,F()r c(.)ml)nrison, rh(' true signal is sh()wn in t.h('

"d(_t.('ctor unl)l.oclce(l" eXl)eriln(mt of Fig, 21tr,

Fiually, I would like t(_ point ()l.tt, st)nit, 1)ft)Sl)Ce.ts t'or (.'xtending this w()rk ut t,lie hd-

vanccd Photon Source. Inelttst.ic phot, ou sc'a/.tcri_tg is _tli importunt and n_tt_u'M (:Xl)erim('nt

for tlt(' APS. One lll('ftSlIl'(?S th(_ dymmiic resl)()nse of au l-it(7)lll()v(?r I.l,wide range (.)fn_()m(m-

rum and energy transfer. \V(.' have seen th_tt ii)r inner shell explorn.ii(m t.h(' high 1)h()t()n

energy (50 - 100 keV) t.hat, will 1)e avMlable at the APS is requir(,d. The high flux of an

intense synchrot.r(,n source lnlfli(:s lh(' ol.)sm'v_tti(m of this w(.'ak 1)roc(,ss rc_t(lily achievM)l(,,

and ('au l(md tc) u data collection tim(, n(lvaltte_g(_ over l'adiution fron_ radi()_('ti','(, s()urc(_s.

\Vit h(mt fiu()r(,s(:(m('e coin(:i(l(,uc(, ther(, is un iuim(,(li_tte 1)()t(mtiM f()r higl_ly iu_l)rov(,d _m-

• ergy resolution which niight l(,_td 1() thr(,sh{_ld studies und th(_ (,xplorntion of corr('la l i()n

_, effects. With ttuorescence (:oincid_,ucc the gaiu in fl_x n_ny also 1)(_iml)ort unt. For ex_unl)h',

one can ilnugine replaci_lg (mr solid targets, ttn(l their distracting nmltiatoni pr()('(,ss(,s, '_

with gas tal'g(_ts. In future (:oinci(l(,nt-1)r()du(:t VXl)(,rinwnts we shmtl(l r('(:ognizc t.lw 1)ossi -

ble dis;tdvant_ge of a pulsed so_u'('(' ii' we _r(' l(,oldng for a v,'e_tk coinci(h,nc_' signM in the

I)l'(_s(i'n('o ()f iulmlse a('ci(l(mtM l:_n('l_gr(_m(1,,. B_tt the direct _tl)l)r(mcl_ t() ln('_tSlll'illg _t('('i-

(lentM (,ffe('ts can succ¢,(:,d. And, rh(' t._'('l_ni(l_' (_t'using a flu()r(._s('(,n('(, trigger will ('()nt i_u(,

379

1 °to provide a valu_ble means of dissc, cting the (ly mlmC structure of _ttoms with in_,lastic

x-ray scattering,

In conclusion, I would like to express lny al)preci_Lt.ion to my collal)oratc_r, Dr. Vinccl:lt

Marc h(_'tti, who obtained all of (:)111're.suit, s.

12(,t'eri_m,cs

lP,hl, Platznmn in Elementary Excitations in Solids, Molecules, and Atoms,

cd. by J. D(:vl'ces(:_ ct al. (London, Plt:nun l, 1974) v, 1, 1), 31.

uI(. Namikawa and S. Hos(:)ya, Phys. 12(,v. Lc,t,ts. 53, 16(/6 (1984) and 57, ]501 (1986).

aT. Fukamachi an(l S. Itos()ya, Phys. L(.,tt. 38A, 341 (1972).

'IV. hlarch('tti and C. Fran('k, Phys. II(,v. A39,647 (1989).

'_V. Mar(:h(_tti and C. Franck, 12,ev. Sci. Instrum. 59,407 (i988).

_V. Marchetti and C. Franck, Phys. I'/(:_v. L_:,t,t. 59, 1557 (1987).

7S. himmin(nl, Phys. II.ev. Lctts. 57, 1501) (1986).

sS. Malmincn, K. Ham_Llain(:ll, and J. Gra(!_tf(:, Phys II(:','. B41, 122,1 (1990).

380

@E,q T

" Fig. 1" Inelastic X-Ray Scattering: a) Physical Space, O: scattering angle and T: target"

b) Diagrammatic (see text).

i

381

SI

Fig. 2: Dynamic Structure Factor (S) as a Function of Energy Transfer(E) for a Free

Electron Target at Fixed Momentum Transfer.

............Fig. 3" Dynamic Structure Factor as a Function of Energy Transfer for a Bound Electron

Target at Fixed Large Momentum Transfer.

S

,,,_EEo

Fig. 4: Dynamic Structure Factor as a Function of Energy Transfer for a Bouni Electron

Target at Fixed Small Momentum Transfer. E0 is the threshold energy (see text).

382

S

-- EE0

Fig. 5' Hypot.hetical Dynamic Structure Factor as a Function of Energy Transf_:r fl_r a

Bound Electron Target at. Fixed hl tc_'medi"_te ._Iomentum Transfer.

S

0

I

J_-_-_-_ [

Fig. G: Dynamic Structure Factor as a Function of Energy Transfer at Fixed Intori_w.diat,,

Momentum Transfer (for an Inner SheLl). No.tc the overlap between spectra from inner (I)

and outer(O) shell electron.,,.

383

/Q

.////.//// J////// /_ I//////

I

_ K -...o---@-K _K

Fig. 7: Inelastic Scattering of the I,_-Shell followed by Fluorescence Emission. I" incident

photon, S: scattered photon, and F: I,_-fluorescence photon.

384

a) D

YT

" _ I............] IM

b) _ FPD

T

Fig. 8" Schematic PhysicM Layout for Inelastic X-Ray Scattering in Coincidence with

Fluorescence Detection. a) Side view. b) Top view. T' target, SPD" scattered photon

detector. FPD: fluorescence photon detector_ and IM: ionization chamber beam monitor.

: Shielding not shown.

" 385

SPD FPD

---4 1----

Fig. 9' Outline of Electronics for Inelastic Scattering in Coincidence with Fluorescence

Detection. SPE)" scatter(,d photon detect(n', FPD' fluorescence photon detector. SCA"

stool,, channel analyzer, G" linear gate, and PHA: pulse height analyzer.

386

Adapted from Phys. Rev. A ._..9_,647 (1989)

Rate r

2

1

0

40 50 60 70

E,_,,,, (keV)

Fig. 10: ._Ieasured (points (+ 15 % absolute scMe uncertainty)) and CMculated (line) Spec-

trum of Inelasticakly Scattered Photons in Coincidence with I(-Fluoresconce as a Function

of Scattered Photon Energy at. a Fixed Scattering Angle (90°). Copper target. S('att(_ring

rate is the triple differential scattering cross section (see text.) in units of 10 -'t b/(keV-sr'-').

E,,, is the incident energy.

387

Rate -:

. iJL_r-_ I .0 _z ------- i " "

s- _ T E{,_ /!

]

0

50 40 50 60 70

(k V)

Fig. 11' Inelastic Scattering Spectrum in Cohlcidence with Ii-Fluorescence at Different

hlcident E lergies. Ordinate as iii Fig. 10. 4- 40 % M)sohite scale uncertainty.

388

Adapted from Phys. Rev. A _,, 647 (1989)

Rate

6

/_

I

0 .-_[ i--_-.... +---- -- K! I t T" J" '

i i ' ' ' +5 ' _ 0_ '7.5 8.0 8. 9.0 9.5 I .0Energy (keV)

Fig. 12: Detecting Photon Decay Spectra (Fluorescence)in Coincidence with Inelastic

Scattering (points) and without Coincidence (line).

. 389

Adapted from Phys. Rev. Lett. 59, 1558 (1987)

Rate

il j. T . ! + :, _ ._. _

i >6 (b

5t ,. _ T 'T T i,, ....... :-, I i _. ,i

(c)

+ Tiii_'

t !,13 I t

o-'" ...... • ._'---._-_'_1 T T I

J- 111,,|

_0 +0 50 60 70

E_,, (keV)

Fig 13: 2Ieasured (+ 40 % absohtte scale uncertainty) and Calculated Spectrum of Inelas-

tica_y Scattered Photons in Coincidence with I(-Fluorescence as a Function of Scattering

Angle. Ordinate as in Fig. 10. The scattering angle and corresponding momentum trans-

fer for elastic scattering (q0) times the I(-shell orbital radius (a) are as follows: a) 0 =

118 ° , qoa = 1.11: b) 88 °, 0.90; c) T0°, 0.74; and d) 49 °, 0.53.

390

Adapted from Phys. Rev. Lett. 53, 1606 (1984)

Rate 41 R

,! Co" 2_

. ' '" o /

or-' " .... '" ' ",.-'': ....50 60

qf

; C'

_! Fe! ' "" a

c '.T.'/" \/_\DT.,XE_,, Il! .,.....0 '"' • -. .. .. i

= 4 "56 _

(keV)

Fig. 14: Inelastic Scattering Specu'um in Coincidence with K-Fluorescence measured t)y

Namikawa and Hosoya (Phys. Rev. ietts. 53, 1606 (1984)) for Copper and h'on.

391

Adapted from Phys. Rev. B 4._3.1,1224 (1990)

Rate ,_oo, ' - " 1

:oo_ ,zz_r--li'U_I I_ iz -- , ' I _ __ Iz,_ -zr', i : I _ t , -'

:0 30 48 SO

Zr,

01_ - "r.,.TT_"=" ;" .Z-xz-;":0 30 4O 50

(keV)

Fig. 15' Inelastic Scattering Spectrum in Coincidence with K-Fluorescence _Ieasured

(points) by Manninen, Hamalainen, and Graeffe (Phys. Rev. B41, 1224 (1990)) for

Copper and Zirconium. Incident energy is 59.6 keV.

392

Fig. 16" True (T) and Accideutal (A) Events.

393

Adapted from Rev. Sci. Instrum 59, 407 (1988)

Rate

1000

a)

5OO

50C

Fig. 17: Coincidence Spectra Produced with Both Detectors Sensitive on tile Same CHESS

Pulse (a), Successive CHESS Pulses (b), and the Difference Spectrum (c).

394

Adapted from Rev. Sci. Instrum.5.9.,407 (1988)

Noise / Signal

_,=0

\

\'\

\,

\,\,\

_,=20

0.1 0.2 0.5 1.0 2,0 5,0 10.0

Intensity

Fig. IS' Expected Noise to Signal Ratio as a Function of Beam Intensity versus ), :_--=

Accident,_fl Coincidence Rate / True Coincidence PLate. Curves scaled to agree at, a rcf rcnce

= intensity.

_, 5

Rate

_6ooa,)

6oo- b)

0 _--'_ "_• f ,, I , | ,, , _, , I

0- 20 40 60 80 100

E,_,,,, (keV)

Fi,,;. 19" Sp,,¢:tra Detecte_l by Scattered Phot_n_ Detector without Fluorescence Coin,:i_h:m'e

(Sin_,l,, e.,_ Sp_ctra) with (a) and without (b) T_r;p_t..

396

B,,

_ __\ 11 _L _ -- S

P°

: Fig. 20' Physical Layout of Control Exp(:riment to ._Ieasure Detector Crosstalk. Lines

; with arrows indicate possible path for crosstalk event. B" blocker. T' target, S: shi_!:lcliilg,

SPD' scattered photon detector, and FPD' fluorescence photon detector. See text for

det_dls.

397

Adapted from Rev. Sci. Instrum .__9.,407 (1988)

Rate

IItt I

-60 -

_o ,o _o _o _o _o

E,_.,,,, (keV)t

Fig. 21' Coincidence Spectra from Crosstalk Control Experiment. The scattered photon

detector's view of rh,. target is unblocked for a) and blocke_l _r b).

398

Closing Remarks.

Work_;hop on Atomic Physics at the Advanced Photon Source.

Ivan Sellin, the University of Tennessee, Knoxville, and Physics Division,

Oak Ridge National Laboratory.

Friday, March 30, 1990.

Since it is scarcely possible to cite more than a few, perhaps

unrepresentative examPles of many of the fine results and ideas presentedin the last two days in the I0 minutes I h._ve available, I shall

concentrate instead on extracting elements of basic wisdom we have heard.

Conventional though some of this wisdom may be, we should recall that

wisdom becomes conventional because it is so often right, and therefore

worth heeding.

Brant Johnson recalled that several of the topics we have heard discussed

were already featured in a workshop held on atomic physics at synchrotron

radiation facilities held 1_srly I0 years ago. Photoionization of ions isa leading example, lt is well to remember that the main reason for this is

the still prevailing lack .f availability of facilities for studying such

phenomena, unoerscoring again the persistent, acutely felt needs in our

community for facilities which can assist us in acquiring appropriate

capabilities. There is also an advantage in the delay" it has given

theorists like Steve Manson and G6ran Wendin the ci_ance to study many

detailed examples, to point the way to experimentalists to particularly

important problems that will lead to new insights, and to work out explicit

results which c_n then be compared with new experiments. Thus delay is not

without its utility, so long as it does not outlast the limits of ourinterest.

When new, very large, and therefore nearly unique facilities like the APS,

ESRF, or SPRING come on line, what difficult new conditions for conducting

experiments might w_ face? Speaking as a person whose past experience lies

mainly within the area of accelerator based atomic collisions experiments

pursued at popular heavy ion accelerator facilities, one of the most

difficult tasks is procuri_g enough beam time for experiments. In s_eking

a large enough quantity of beam time per successful applicant, program

advisory committees inevitably ask, "What is ther_ that makes this facilityuniquely useful for your experiment? Why can't this experiment be done at

someone else's facility?"

Uniqueness _guments therefore count for a cry great deal in achieving- good access _o facilities and to beam t_me. lt is thus well to ask, what

is truly unique about a facility like APS?

In a casual conversation I had a year ago with the director _f a large vuv

" ring, I _sked him what he thought a machine like the APS could uniquely do

to advance atomic and molecular physics chat other machines could not

match. Qua iifying his answer by noting that it was likely to be prejudicedby his own long term commitment to probing _alence elec_ron behavior, his

reply came down to this' unless one has to access specifically K shell

electrons of heavy elements to achieve specialized experimental goals, thensince the larger v_,v machines will be able to access the L shells of most

of zhe elemer.cs in the periodic table, there is _ot much to be gained from

higher energy synchrotron radiation facilities for the majority of problemshe would consider "importent".

399

We can of course immmediately agree with Dar____!tof this argument. We heard

from Professor Crasemann about challenges of relativity and qed that are of

course best attacked by studying the most deeply bound levels possible.

From Professors Wendin and Franck, we heard about study of x-ray inelasticand Compton processes for which again hard photons are quintessentiallysuitable.

However, the argument fails to acknowledge a most significant point' the x-

ray intensity is greater at al___lenergies at facilities in the APS class,

not just the hard x-rays for which such rings are optimized. How important

this feature may become is underscored by the many comments speakers have

made concerning how tenuous are 'the gas targets atomic physicists use, andhow near zero are ion densities in ion photoionization experiments. Of

course, not all of this intensity gain will benefit ali experiments, sincethe total flux rather than the brilliance will benefit. But there are

broad classes of important experiments where flux is key, and for those

facilities like APS, ESRF, and SPRING the high flux available will be key

as weil. Some experiments, such as the trapping experiments discussed by

Prof. Church, simultaneously use both soft and hard photons; for such

applications a machine with APS capabilities will be very effective.

Modern progress in atomic and molecular physics has been characterized by

increasingly differential experiments, achieved by use of coincidence

techniques, high en=rgy and angular resolution spectrometric devices, and

position sensitive detection. Several speakers here have emphasized theneed for future coincidence experiments, for example Steve Manson in

pointing out the need for studying the angle and photon en=rgy dependence

of two electron processes above threshold; and Manfred Krause who

additionally commented on the potential value of coincidence techniques in

looking, for example, at various double hole processes. From two other

speakers, Drs. Franck and Levin, we learned about the success already

achieved in adapting coincidence techniques in two quite different

applications.

Such techniques piace an enormous premium on intensity °- the more

dilferential or multiparameter they get, the greater are the intensity

demands. Thus flux that promises to emerge from the APS and like

facilities may make many experiments possible which lower flux facilitiescan never reach.

Fortunately, as x-rays get harder, and inner shell transitions become

increasingly dominated by x-ray decay channels, the intensity demands posed

by multiparameter coincidence experiments are eased by the availability of

efficient, dispersive x-rays detectors such as SiLi and GeLi detectors.While such detectors have the limitations of limited resolution and the

slow pulse rise times which make their use in coincidence experiments

problematic, in many cases the advantages of providing high solid angle a_d

simultaneous energy dispersion are likely to make them valuable tools.

The subject of timing has not been emphasized at this workshop. However,for all of us who contemplate timing experiments, using time of flight

spectrometers, coincidence techniques, or both, it will be important to

have good timing capability. Often this is available ali too rarely, for

most users prefer ali buckets to be filled, not just the single buckets

characteristic of most timing runs at present synchrotron radiation

facilities. I would like to call attention to the pressing need for

development of shutters which can send one burst of light do_ a beam line

400

r

while the ring itself is in standard multibunch operation, shutters wllich

should also provide a synchronous timing signal.

In the time available to me here, I have not been able to summarize the

extensive catalog of future experimental possibilities which various

speakers have presented. Perhaps this effort was not needed, since Dr.

, Kimura's comprehensive account of the highly variegated plans of his

Japnnese colleagues seemed to me to blanket the interests of many of us

ve_ J well. The Japanese study group,s identification of multi-charged ion

structure and collision problems seemed to contain many entries which

perhaps interest many, if not most of us. One such topic mentioned by

Kimura but not covered elsewhere in the workshop is the use of multicharged

ions produced by SR radiation as a source of secondary beams in studyingcollisions of eV energy multicharged ions with atoms and molecules. As

those of you acquainted with ion-atom collisions physics may know, very

promising, similar studies are already underway using MeV beams of highly

charged projectiles as the source of ionizing radiation, in several

laboratories, including our own. It will be very interesting to see howmuch better one may be able to do using SR radiation instead.

The final duty of any workshop summary talk is to express appreciation for

the efforts and achievement of the hard-working organizers in providing astimulating, enjoyable visit here for us all. I would like to close the

workshop by calling for a round of applause in their behall.

- 40 I/_L

PROGRAM

WORKSHOP ON ATOMIC PHYSICS

ATTHE ADVANCED PHOTON SOURCE

March 29-30, 1990

- Argonne National LaboratoryPhysics Building- 203 Auditorium

Argonne, Illinois

403

Thursday, March 29, 1990

8:30 a.m. MOI_ING SESSION I

Chair: Gordon Berry, Physics Division, Argonne National Laboratory,Argonne, Illinois

Welcoming Remarks (10 min)Alan Schriesheim, Director, Argonne National Laboratory,Argonne, Illinoi_

Introduction to the Advanced Photon Source (40 min)David Moncton, Associate- Laboratory Director for theAdvanced Photon Source, Argonne National Laboratory, Argonne,, .

Illinois

Atomic Physics with Hard Synchrotron Radiation: Introduction andOverview (40 rain)

Bernd Crasemann, Chemical Physics Institute, University ofOregon, Eugene, Oregon

X-ray Photoionizstion of ions and Atoms: New Frontiers (40 min)Steve Manson, Department of Physics, Georgia State University,Atlanta, Georgia

10:40 a.m. Coffee Break

11:00 a.m. MORNING SESSION II

Chair' Uwe Becker, Technical Institute of Berlin, West Germany

Photoionization of Excited Atoms and Ions Using Synchrotron Radiation:Present Status and Future Trends (40 min)

Francois J. Wuilleumier, Laboratoire de Spectroscopie Atomique etIonique, et Laboratoire pour l'Utilisation du RayounementElectromagnetique, Universite Paris-Sud, Orsay, France

Atomic Physics at the Advanced Light Source (40 min)Alfred S. Schlachter, Lawrence Berkeley Laboratory, Berkeley,California

12'20 p.m. Lunch in the Argonne Cafeteria, Dining Room C

4o4

Thursday, March 29, 1990

1:20 p.m. AFTERNOON SESSION I

Chair: Yohko Azuma, Physics Division, Argonne National Laboratory, ,/_Argonne, Illinois

The RIKEN-JAERI 8-GEV Synchrotron Radiation Project SPring-8 (40 min)Yohko Azuma, The Institute of Physical and Chemical Research,RIKEN, Japan

Photoionization of Ions andthe General Program in Atomic and MolecularPhysics at Daresbury (40 rain)

John B. West, Daresbury Laboratory, England

Multicharged Ion Research Using the Advanced Photon Source (40 min)David A. Church, Physics Department, Texas A & M University,Texas

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3:20 p.m. Coffee Break

3:45 p.m. AFTERNOON SESSION H

: Chair: Larry Toburen, Batelle Pacific North-West Laboratories, Richland,Washington

Atomic Physics with Hard X-Rays: Perspectives and Opportunities (40 min)Goran Wendin, Institute of Theoretical Physics, ChalmersUniversity of Technology, Goteborg, Sweden

Thoughts on Future ESSR Studies of Inner Core Levels (40 min)_

Manfred O. Krause, Oak Ridge National Laboratory, Oak Ridge,Tennessee

: Beam Line Considerations for the Experiments with Highly-Charged Ions(40 min)

Brant M. Johnson, Physics Department, Brookhaven NationalLaboratory_ Upton, New York

5:45 p.m. Adjourn

Buses to the Hotel, and then to the banquet (returning to the hotel- about 9 p.m.)

: 6:45 p.m. _ and Banquet_ at Carriage Greens Country Club_

4O5

Friday, March 30, 1990

8:30 a.m. MORNING SESSION i

Chair: Pedro Montana, Advanced Photon Source, Argonne NationalLaboratory, Argonne, Illinois

Applications of High-Brilliance X Rays from Insertion Devices at the APS(40 min)

James P. Viccaro, Advanced Photon Source, Argonne NationalLaboratory, Argonne, Illinois

Can a Powerful Source (APS) Cast Useful Light on Atomic Hole StateProcesses? (40 min)

Paul L. Cowan, National Institute of Standards andTechnology, Gaithersburg, Maryland

Studies of Clusters (30 min)Wolfgang Eberhardt, Exxon Research and Engineering, Annandale,New Jersey

10:20 a.m. Coffee Break

11'00 a.m. MORNING SESSION II

Chair: Indrek Martinson, Lund University, Sweden

Atomic Physics with Hard Synchrotron Radiation: Report from the Japanese"Working Group" (40 min)

Masahiro Kimura, Department of Physics, Osaka University,Osaka, Japan

11:45 a.m. Tour of the Advanced Photon Source model

Buses to building 360, returning to the cafeteria

12:30 a.m. Lunch, Argonne Cafeteria, Dining room C

4o6

i

Friday, March 30, 1990

1'30 a.m. AFI_RNOON SESSION

Chair; Noura Mansour, Physics Division, Argonne National Laboratory,Argonne, Illinois

Argon-Ion Charge Distributions Following Near-Thereshold Photoionization

(30 min) 7_,.Ion C. Levin, Physics Department, University of Tennessee, _Knoxville, and Physics Division, Oak Ridge National Laboratory,Oak Ridge, Tennessee

Resonant Nuclear Scattering with Synchrotron Radiation (40 min)John Arthur, Stanford Synchrotron Radiation Laboratory,Stanford, California

Revealing Inner Shell Dynamics with Inelastic X-RayScattering (30 min)Carl Franck, Department of Physics, Cornell University, Ithaca,New York

3:10 p.m. Closing RemarksIvan Sellin, Physics Department, University of Tennessee, Knoxville,and Physics Division, Oak Ridge National Laboratory, Oak Ridge,Tennessee

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3:20 p.m. Adjourn

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4O7

WORKSHOP PROGRAM AND ORGANIZENG COMMI'ITEE

H. Gordon Berry

Yoshiro Azuma l Argonne Physics DivisionNoura Berrah Mansour

Yohko Awaya, RIKEN, JapanDavid Church, Texas A&M UniversityBernd Crasemann, University of OregonJoseph L. Dehmer, Argonne Biological, Environmental and

Medical Research DiLvision

Keith Jones, Brookhaven National LaboratoryAlfred Schlachter, Lawrence Berkeley LaboratoryIvan A. Sellin, University of TennesseeFrancois Wuilleumier, Universite Paris-Sud

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PARTICIPANTS

Ercan E.Alp UweBecket DonaldA.Carter

AdvancedPhoton Source Departmentof PhysicsPN 3-2 Marketing

ArgonneNationaJLaboratory TechnicaJUniversityof B_din Optic-ElectronicCorp,._rationBuilding360 Hardenbergstr.36 11545Pagemill9700 South CassAvenue D 1000Bedin12 Dallas,TX 75243

Argonne, IL 60439 WESTGERMANY

IgnacioAivarez MichaelJ. Bedzyk Ronald GeorgeCavetlLaboratodo DeCuemavaca, CHESS Department of Chemistry

InstitutoDe Fisica, Unam CornellHigh Energy SynchrotronSource Universityof AlbertaAl:x:lo,Postal 139-B Cornell University Edmonton,AttaT6G 2G2Cuemavaca, Morelos62191 Wilson Laboratory CANADAMEXICO Ithaca, NY 14853-8001

JohnArthur H. GordonBerry KwokTsangCheng

Stanford Synchrotron Radiation Laboratory Physics Division Lawrenco LivermoreNational !._borator'j.Bin69 ArgonneNa_onaJLaboratory P.O. Box 808P.O. Box 4349 Building203 Livermore,CA 94550Stanford,CA 9430,5 9700 S. Cass Avenue

Argonne,IL 60439

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Hirosawa 2-1 9700 South CassAvenue 9700 South Cass Avenue

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= Building 2C2 Building3609700 South Cass Avenue 9700 So,JthCassAvenue

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Ben _dCrasemann Patrick O. Egan RuprechtHaenselPhy.,'.icsDepartment L-Division ESRS

Universityof Oregon LawrenceLivermore National Laboratory GrenobleEugene,OR 97403 L-45 FRANCE

P.O.Box 808

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A,rgonne National Laboratory PhysicaJResear,,;h Universityof Nortre DameBuilding 203--C125 ArgonneNational Laboratory NotreDame, IN 46556_3700South CassAvenue Building221a,rgonne, IL 60439 9700 South CassAvenue

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Argonne National Laboratory Cornell University University of ChicagoBuilding203-B161 ClarkHail 5747 South Ellis Avenue

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_im PatrickDinneen Jean W. Gallagher 'RussellH.HuebnerPhysics Standard Reference Data Advanced Photon Source

Argonne National Laboratory National Institute of Standards & Tech. Argonne National LaboratoryBuilding203 Physic" A323 9700 South Cass Avenue9700 South Cass Avenue Gaithersburg, MD 20899 Argonne, IL 60439Argonne, IL 60439

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Arg,unne, IL 60439 ITALY

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Physics Division Chem;stry Division Department of Applied Science

Arsonne National Laboratory Argonne National Laboratory Brookhaven National Laborator'/Builcing 293 Building200 Building 8159700 South Cass Avenue 9700 South Cass Avenue Upton,NY 11973Argonne, IL 60439 Argonne, IL 604.39 ,

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F,oute 22 East Natural Sciences Research Counse_ Building815AnnandaJe,NJ 08801 P.O Box 6711 Brookhaven National Laboratory

11385 Stockholm Upton, NY 11973SWEDEN

4!2

ElliotKanter Scott D.Kravis DanLegniniPhysics Division Physics Dep_."l_nent Advancad Photon Source

Argonne National Laboratory Texas A&M University Argonne Nal_onalLaborator,!, Building 203 TAMU Building 360

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Teng _k Khoo CharlesKurtz Jon C. Le'4n

Physics Division Physics Division University oi Tennessee/ORNLArgonne Nadonal Laboratory Argonne National Laboratory 10016 Cedar Croft CircleBuilding 203-F145 Building203 Knoxville, TN 379329700 South CassAvenue 9700 SouthCass AvenueArgonne, IL 60439 Argonne, IL 60439

• Ali M.Khounsary Mickey D.Kut:zner GuokuiUu

Advanced Photon Source Physics Department Chemistry Division

Argonne National Laboratory Andrews University _rgonne National Laboratory-Building 360 Bemen Spnngs, MI 49104 Building 200, M-1699700 South Cass Avenue 9700 South Cass Avenue•Argonne, IL 60439 Argonne, IL 60439

MasahiroK]mura TuncerM.Kuzay Zhengtian Lu

Department of Physics Advanced Photon Sourc_e Physics Division

_saka University ArgonnJ National Laboratory Argonne National Laboratory1oyonaka, Osaka 560 Building3_0 Building 203

-JAPAN 9700 South Cass Avenue 9700 South Cass AvenueArgonne, IL 60439 Argonne, IL 60439

orn KJippert Victor H.S.Kwcng Steven T.Manson

',dvanced Photon Source Physics Department Physics & Astronomy

.rgonne NatJonatLaboratory University of Nevada. Las Vegas Georgia State University:'ullding 360 4505 Maryland Pa,nkway Atlanta, GA 30303- 700 SouI_ Cass Avenue LasVegas, NV 89154__,rgcnne,IL 60439

ac!av O. Kostroun Jayan_ Labiri ,",louraB.Mansour

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.,/ard Laboratory Southern College of Technology A,'gonne National La_orator'!omeil Universl_ 2200 South Madetta Parkway -muilding203

_aca, NY 14z353-,'-701 Manet'ta,GA 30060 9700 South Cass AvenueArgonne, IL 604-39

anfred O. Krause _ng LaJ Vincent Jame._,Marchet'ti

'-hemis_'t Department Coatings Department Prog. in Nuc. Science and E_gme,_ring

ak F_id_eNational Laboratory Olmtic-E!ec_'onicCorporation 'Nard Laboratory-.Jil¢ing450_JN 11545Pagemill Cornell UniversityO. Box 2008 Dallas, "IX 75243 Ithaca, NY 14.853_k Fddge,TN 37831--6201

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IndrekMartinson Bengt Johannes Olsson David G. Rognlie

Department of Physics Synchotron Radiation Center/CSRF Blake industries Incorporatied

University of Lund University of Wisconsin-Madison 660 Jerusalem RoadSo!vegatan 14 3731 Schneider Drive, FIoute 4 Scotch Plains, NJ 07076S-22362 Lund Stoughton, Wl 53589--3097

SM/EDEN

Rulon Mayer David John Pegg Alfred S. Schlacnter

Physic'_ Oepartm, ent Department of Physics ALS

U.S. Department of Commerce University of Tennessee Lawrence Berkeley LaboratoryNational Insti,'ute of Standards & Technology Knoxville, TN 37996 MS 46-161

Physics Building, Room A 141 Berkeley, CA 94720Gaithersburg, MD 20899

Dennis Miils Gilbert Jerome Per'low Alan Sc.h,qesheim

Advanced Phuton Source Physics Division Director

Argor:,,e National Laboratory Argonne National Laboratory Office of the Direc*,orBuilding 360 Budding 203 . Argonne National Laboratory9700 South Cass Avenue 9700 South Cass Avenue Building 201

Argonne, IL 60439 Argonne, IL 604.39 9700 South Cass AvenueArgonne, IL 60439

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Advanced Photon source Instrument Division Physics

Argonne National Laboratory Baker Maqufacturing Company University of Tennessee,ORNL9700 south Cass Avenue 133 Enterprise Street Building 5.500

Argonne, IL 60439 Evansville, WI 5371 1 P.O. Box 2008Oak Ridge, TN 37830--3377

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A_gonne Nation_ I.._boratory Argonne National Laboratory The University of ToledoBuilding 360 Building 203-C-141 2801 West Bancroft Street9700 South Cas._ Avenue 9700 South Cass Avenue Toledo, OH 43606

Argonne, IL 604.."9 Argonne, IL 604.39

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Departmer_t of Physics Physics Advanced Photon source

Uppsala University Argonne National Lmi::orato ry Argonne National Laccrator'tBox 530 Eulicing 203 Building 360

S--751 21 Uppsala g700 South Cass Avenue 9700 Sou_h Cass Avenue

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Chofu Tok?o 782 Builcing 360 Budding 360

JAPAN 9700 South Cass Avenue 9700 scutch Cass Avenue

Argonne, IL 60439 Argonne, IL 60439

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ElizabethStefanski MarvinJ. Weber Wenbing YunAdvancedPhoton Source DepLof Chemistry & Materials Scf. Advanced Photon Source

Argonne National Laboratory Lawrence Livermore National Lab. Argonne Nadonal Lat_ratoryBuild!:',g360 L..326 Budding3609700 South Cass Avenue P.O, Box 808 9700 South Cass Avenue

Argonne, IL 60439 Livermore,CA 94.550 Argonne, IL 60439

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Office of Basic Energy Sciences Institute of Theoretical Physics Physics Division

,_ Office of Energy Research Chalmers University of Technology Argonne National I_ab_raloryU.S. Department of Energy/DC S-41296 Goteborg 9700 South Cass Avenue

Washington,DC 20545 SWEDEN Arcjonne,IL 60439

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K_mHwaTan TimothyAlanWhitney/

-_ Canadian Synchrotron Radiation Facility Chicago District Office,B 3725 Schneider Drive Cray Research, Inc.

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Richard N.Thudium DavidW'mn. Analytical Science Physics Department

GoodyearTire & Rubber Company Andrews University142 Goodyear Boulevard Bemen Springs, MI 49104Akron, OH 44305

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Larry H.Toburen Gregory WoodardRsdietogicaJ Physics Depar't_ent Physics DepartTnent

Battelle Pacific Northwest Laboratory Andrews UniversityP.O Box 999 Berden Spdngs, MI 49104Richland,WA 99352

Jim Viccaro UndaYoung

_- Advanced Photon Source Physics Division

_ _,rgonneNational Laboratory Argonne National LaboratoryBuilding 360 Builcing 2039700 South Cass ,_venue 9700 South Cass Avenue

Argcnne, ", 604.39 Argonne, IL 60439

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atomic physics at the advanced light source [workshop rpt]

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