spectroscopy of the heaviest elements

Spectroscopy of the Heaviest Elements

Partha ChowdhuryUniversity of

Massachusetts Lowell

outline

Shells and their magicgaps, spherical and

deformedstability, synthesis, spin,

spectroscopyExperimental techniques

reaction mechanismsdetectors (arrays and

auxiliary)Prompt and delayed spectroscopy Looking ahead

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let's begin at the (heaviest) end

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the superheavy island of stability293117

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frontiers in superheavy synthesis

249Bk + 48CaDubna gas filled separator70 days of Ibeam~450 pnA5 eventsσ~1 picobarnChowdhury VECC­NNCAFE Dec 17, 2010

which theory has the right magic?

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spherical magic gaps from a deformed perspectiveProtons Neutrons

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R. Chasman et al., Rev. Mod. Phys. 49, 833 (1977) Woods-Saxon

spherical magic gaps from a deformed perspectiveProtons Neutrons

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R. Chasman et al., Rev. Mod. Phys. 49, 833 (1977) Woods-Saxon

Cables

A~250

map of the neighborhood

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spectroscopy frontier : the heaviest elements

Herzberg and Greenlees, Prog. Part. Nucl. Phys. 61, 674 (2008) Chowdhury VECC­NNCAFE Dec 17, 2010

known levels

≤5

≤10

≤20

≤50

>50

=0

complementary reaction mechanisms

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N

Z fusion­evaporationdeep­inelastic

in-beam spectroscopy of (super) heavies

208Pb (48Ca,2n) 254No σ ~3 µb, ~9 pnA

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P. Reiter, T.L. Khoo et al., PRL 82, 509 (1999)

Gammasphere + FMA

Recoil Decay Tagging

14+

254No (contd.) at Argonne and Jyvaskyla

S. Eeckhaudt et al., EPJA 26,

227 (2005)JUROGAM/RITU/

GREAT

recoil gated

singles

recoil gated γ

−γ

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GS + FMA219 MeV

48Ca

P. Reiter, T.L. Khoo et al., PRL 84, 3542 (2000)

JUROGAM/RITU/GREAT

20+

246Fm : in-beam spectroscopy at the limits

J. Piot et al., FINUSTAR3, Rhodos, Greece, Aug 2010

JUROGAMII/RITU/GREAT ~10 nb, ~70

pnA

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K-isomers and (super) heavies

Single particle energies and shell gaps beyond Z=82 and N=126

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Testing symmetries at the highest oscillator shells

Role of K-isomers in stability of superheavies ?

K-isomers

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8−

9−

10−

11−

12−

K=0

K=8

Symmetry axis

Rcollective

Ω1 Ω2

Κ= ΣΩi

J total

j2

j1

intrinsicj

j2

axially symmetric deformation

high-Ω orbitals near Fermi surface

collective rotation and intrinsic modes compete for yrast status

test symmetry to find limits or use symmetry to probe structure

208Pb ( 48Ca,2n) 254No with GS+FMA

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S.K. Tandel et al., Phys. Rev. Lett. 97, 082502 (2006)

constraining models for superheavies

­8.10­7.97­7.59

­6.44­6.32­6.24­6.19

­4.50­4.08

­3.29

­2.60­3.03

­2.06

­1.13

7/2[514]1/2[521]

7/2[633]3/2[521]

9/2[624]

5/2[512]

9/2[505]

11/2[725]

5/2[622]7/2[624]9/2[734]

1/2[620]3/2[622]7/2[613]

protons

neutrons

E (MeV)

Fermi level

i13/2

h9/2f5/2

­4.86 1/2[400]­4.93 5/2[642]

N=152 Z=102

low Kπ=3+ energy possible if calculated proton energies very close to Fermi level and pair gap correctly determined

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1/2[521] level is the one from the f5/2 orbital above the Z=114 shell gap !

206Pb( 48Ca,2n)

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204HgS( 48Ca,2n)

continuing with fusion-evaporation Jyvasky

la

Argonne

208Pb( 50Ti,2n)

Berkeley

complementary reaction mechanisms

209Bi (1450 MeV) on 248Cm207Pb (1430 MeV) on 249Cf208Pb (1430 MeV) on 244Pu

~15% above Coulomb barrierATLAS at ANL + Gammaspherebacked targets, beam sweeping

Inelastic and transfer reactions with radioactive targets

Complement low-statistics fusion-evaporation Z>100 studies

Follow same neutron orbitals into lower-Z neutron-rich isotones

Earlier successful prompt spectroscopy in Cm and Pu using these techniques

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N

Z fusion­evaporationdeep­inelastic

S.K. Tandel et al., Phys. Rev. C 82, 041301 (R ) (2010)

1450 MeV 209Bi + 248Cm, 1430 MeV 207Pb+ 249Cf X-gamma and cross-coincidences with binary

reaction partnerHigh-spin studies at the highest oscillator shellsHighest-Z nuclei studied via inelastic excitation

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in-beam spectroscopy via inelastic/transfer

Odd-A Cm(Z=96) and Cf(Z=98)

209Bi +

248Cm1450

MeVInelasticU.Shirwadkar,

Ph.D. thesisUMass Lowell

(2009)Chowdhury VECC­NNCAFE Dec 17, 2010

248Cm(Z=96) prompt and delayed

Total projection hypercube

+ prompt time gate

+ gate on GSB

Au coulex

Σ GSB double gates

In-beam Out-of-beam

Kπ = 8 isomer decays in N=150 isotones

Unusual constancy in excitation energy of isomer as well as reduced hindrance factor fν

Robust conservation of K and axial symmetry

ν = ∆K – λ F = t γ

1/2 / t W

1/2 fν = F (1/ν)

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P. Chowdhury, Proc. FINUSTAR3, Rhodes (2010)

GS + CHICO in A~250 region ?

Gammasphere

CHICO HfTh

Scattering angle

Mass

CHICO: M.W. Simon et al, NIM A452, 205(2000)

Unsafe Coulex / Deep-inelasticGS-CHICO @ANL: 1300 MeV 180Hf on 232Th

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CHICO overview: Rochester group

CHICO : Simon et al., NIM A452 (2000) 205

Two hemispherical assemblies10 PPACs each in a truncated cone coaxial with beam direction.12°< θ < 85°, 95°< θ < 168° φ coverage for both assemblies 280° PPAC time resolution 300 ps

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Doppler correction: CHICO + Gammasphere

Doppler correction for Th-like

No Doppler correction

Doppler correction for Hf-like

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U.S. Tandel et al., Phys. Rev. Lett. 101, 182503 (2000)

From Gammasphere to GRETINA

GRETINA+BGS

GS+FMAP.Reiter et al., PRL 84 (2000) 3542

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Segmented crystal36-fold 2 crystal types4 crystals/moduleGRETINA: 7 modules (1π)http://grfs1.lbl.gov

208Pb(48Ca,2n) 254No

From GRETINA (1π) to GRETA(4π)

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GRETINA comes online April 20116 months engineering/comissioning runs at LBNL6 months each subsequently at MSU, ORNL, ANL

GRETA: Gamma Ray Energy Tracking ArrayM.A. Deleplanque et al., NIM A430, 292 (1999)

In the 2007 NSAC Long Range Plan:“…The construction of GRETA should begin upon successful completion of GRETINA. This gamma-ray energy tracking array will enable full exploitation of compelling science opportunities in nuclear structure, nuclear astrophysics, and weak interactions.”

From INGA to -

SummarySuperheavy nuclei : nuclear structure frontier

complementary experimental approachesSynthesis (Dubna, GSI, LBNL, RIKEN,…) Spectroscopy (JYFL, ANL, LBNL,…)

surprising stability against fission at high angular momentaIn-beam spectroscopy

single-particle energies, fission barriersK-isomers (tags, s.p. config./energies, spin-spin residual interactions )

constrain superheavy modelsmeta-stability related to stability ?

Techniques: production and detection fusion-evaporation vs. inelastic/transfer

reactionsseparators and auxiliary detectors (charged

particles, electrons)Detector arrays: the next generation

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