Preliminary results from the measurement of nuclear

isomers and masses in the neutron-rich 160<A<210 region

Ian J. Cullen

University of Surrey

Why Measure Masses?

Mass models vary widely away from measured regions

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.

Current Nuclear Chart

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

Accelerator Schematic9Be 4g/cm2

238U73+ @ 670 MeV/u

Electron Storage Ring (ESR)

Fragments fromthe FRS

Observation of isomeric and ground state decay.

I = 27/2-

Yu. A. Litvinov et al., Phys. Lett. B 573 80 (2003)

I = 7/2-

Ability to measure single particles.

Yu. A. Litvinov, PhD Thesis 2003

Single peaks evolving with time

Yu. A. Litvinov, PhD Thesis 2003

Isomeric energies easily observed.

Yu. A. Litvinov et al., Nucl. Phys. A 756 3 (2005)

First claimed new isomer.

B.Sun et al., Eur. Phys. J. A 31 393 (2007)

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.

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

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.

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