preliminary results from the measurement of nuclear isomers and masses in the neutron-rich 160
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Preliminary results from the measurement of nuclear
isomers and masses in the neutron-rich 160<A<210 region
Ian J. Cullen
University of Surrey
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Why Measure Masses?
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Mass models vary widely away from measured regions
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Storage Ring Technique
• Originally designed to measure masses as far from stability as possible.
• Allow a check of mass models.
• Investigate intrinsic structure of nuclei.
• Work towards deeper understanding of nucleosynthesis via the r-process.
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Current Nuclear Chart
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Present approach
• Technique now being used to search for previously unobserved isomers.
• More sophisticated test of structure models.
Spin isomers at closed shells K-isomers between closed shells
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Accelerator Schematic9Be 4g/cm2
238U73+ @ 670 MeV/u
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Electron Storage Ring (ESR)
Fragments fromthe FRS
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Observation of isomeric and ground state decay.
I = 27/2-
Yu. A. Litvinov et al., Phys. Lett. B 573 80 (2003)
I = 7/2-
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Ability to measure single particles.
Yu. A. Litvinov, PhD Thesis 2003
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Single peaks evolving with time
Yu. A. Litvinov, PhD Thesis 2003
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Isomeric energies easily observed.
Yu. A. Litvinov et al., Nucl. Phys. A 756 3 (2005)
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First claimed new isomer.
B.Sun et al., Eur. Phys. J. A 31 393 (2007)
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Current Work• Search for K-isomers around the
A=200 region, ‘below’ the Z=82 closed shell.
• Main goal: Predicted K=10,18 isomers at 1-2 MeV in 188Hf (compares with K=16, 31-year isomer in 178Hf).
• Search for this isomer is ongoing.
• Other new isomers have been identified.
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New Isomer from current data set
Compare: 1.3MeV isomer in 215Bi, I=(25/2-) T1/2=36.4 s
L.Chen to be published
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Conclusions
• ESR experiment sensitive to isomers with T1/2 > 1s.
• Isomers with energy ~100keV can be resolved.
• Current analysis is ongoing and hopes are high of finding previously unobserved isomers.
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CollaboratorsI.J.Cullen1, P.M. Walker1, Z. Liu1, Yu.A. Litvinov2, L. Chen2,3, K. Beckert2,
P.Beller2, F. Bosch2, D. Boutin2,3, L. Caceres1, R.S. Chakrawarthy4, D. Cullen5, B. Franzke2, H.-Geissel2,3, J. Gerl2, E. Greda2, G. Jones1, A. Kishada5, O. Klepper2, H.-J. Kluge2, R. Knöbel2,3, C. Kozhuharov2, E. Kulich2, N. Kuziminchuk2, S.A. Litvinov2,3, S. Mandal2, M. Matoš6, M.
Montes6, G. Münzenberg2, F. Nolden2, Yu.N. Novikov7, W.R. Plass3, Zs. Podolyak1, R. Propri8, S. Rigby5, N. Saito2, T. Saito2, C. Scheidenberger2,
M. Shindo9, M. Steck2, P. Ugorowski8, G. Vorobjev2, H. Weick2, S. Williams1, M. Winkler2, H.-J. Wollersheim2.
1Surrey University, 2GSI, 3JLU Giessen, 4TRIUMF Vancouver, 5Manchester University,
6MSU East Lansing, 7PNPI Gatchina, 8SU Youngstown, 9Tokyo University