Isomer Spectroscopy of the Heaviest Elements

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Isomer Spectroscopy of the Heaviest Elements
Rod Clark (Lawrence Berkeley National Laboratory)
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Outline

• Motivation for studying structure of heaviest
  nuclei
• K-isomers in Z100 region
• The Berkeley Gas-Filled Separator (BGS)
• Recent results
• 50Ti208Pb?256Rf2n (s20nb)
• 48Ca209Bi?255Lr2n (s300nb)
• Heavy element spectroscopy with GRETINABGS
• Summary

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Motivation

• Single-particle levels ? shell structure
• Next major spherical gaps
• Deformed gaps
• Deformation and collectivity
• K-isomerism
• Rotational structures
• Low-lying vibrations
• Pairing properties
• Multi-quasiparticle states
• Effects on rotation
• Effects on alpha decay
• Effects fission decay

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K-Isomers in Z100 Nuclei
RITU at JYFL
FMA at ANL
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Conversion Electron and Gamma Spectroscopy
S.K.Tandel et al., PRL 97 082502 (2006)
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Berkeley Gas-filled Separator

• ? Large acceptance 45 msr ( 9 vertical, 4.5
  horizontal)
• ? Highest transmission ( NiPb
  70 CaPb 60 MgU 18 )
• ? Large bend angle 70
• ? Lowest background rates ( 40Hz/pmA 20Hz/pmA 10
  0Hz/pmA )

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Focal Plane Detectors
1616 strip DSSD 1mm thick, 5cm by 5cm
1) Recoil implanted in pixel of DSSD 2) Burst of
conversion electrons in same pixel from isomer
decay 3) Gamma-rays in coincidence with electron
burst 4) Recoil decays in same pixel by
alpha/fission
Key idea was to tag on isomer by searching for
burst of conversion electrons and using a single
pixel as a calorimeter.
G.D. Jones (Liverpool), NIM A 488 471 (2002).
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256Rf Z104, N152
50Ti208Pb?256Rf2n at 243 MeV (s20nb), 200pnA,
6 days
Electrons
Gamma Rays
r-e-e-f
r-e-e-f
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H. B. Jeppesen et al., Submitted to PRL
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255Lr Z103, N152
48Ca209Bi?255Lr2n at 222 MeV (s300nb), 300pnA,
4 days
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247Es Z99, N148
g-spectroscopy following a-decay of
255Lr?251Md?247Es
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Eisteinium (Z99) Systematics Re-examined
251Md
251Md
a1
a2
a
g294
g243
g243
g294
0x
247Es
247Es
F.P.Hessberger et al., EPJ A 26 233 (2005) A.
Chatillon et al., EPJ A 30 397 (2006)
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Eisteinium (Z99) Systematics Re-examined
251Md
251Md
?
a1
a2
a
g294
g243
g243
g294
0x
247Es
247Es
F.P.Hessberger et al., EPJ A 26 233 (2005) A.
Chatillon et al., EPJ A 30 397 (2006)
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Transfermium Spectroscopy with GRETINABGS
The best heavy element separator with the best
g-ray detector system
Assumptions for simulation sTOT 1 barn Target
0.5 mg/cm2 Beam Current 50 pnA eg / crystal
0.0067 Mg 10 ? 30.3 kHz/crystal
Energy (keV)
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Summary

• New generation of spectroscopy experiments on
  heaviest elements
• RITU at JYFL, FMA at ANL, BGS at LBNL,
• GABRIELLA at Dubna, SHIP at GSI, VAMOS at
  GANIL
• Decay spectroscopy at BGS able to reach Sg
  (Z106)
• - single-particle states
• - K-isomerism
• - low-lying rotational and vibrational modes
• Prompt spectroscopy with GRETINA at BGS able to
  reach Rf (Z104)
• - rotation versus fission
• - moments of inertia, alignments
• - configuration assignments
• Can modern microscopic theories reproduce
  experiment?

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Thanks!