spectroscopy of the heaviest elements
TRANSCRIPT
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
Chowdhury VECCNNCAFE Dec 17, 2010
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
Chowdhury VECCNNCAFE Dec 17, 2010