1. Preliminary results from the measurement of nuclear isomers and masses in the neutron-rich 160<A<210 region Ian J. Cullen University of Surrey

2. Why Measure Masses?

3. Mass models vary widely away from measured regions

4. 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.

5. Current Nuclear Chart

6. 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

7. Accelerator Schematic 9 Be 4g/cm 2 238 U 73+ @ 670 MeV/u

8. Electron Storage Ring (ESR) Fragments from the FRS

9. Observation of isomeric and ground state decay. I = 27/2- Yu. A. Litvinov et al., Phys. Lett. B 573 80 (2003) I = 7/2-

10. Ability to measure single particles. Yu. A. Litvinov, PhD Thesis 2003

11. Single peaks evolving with time Yu. A. Litvinov, PhD Thesis 2003

12. Isomeric energies easily observed. Yu. A. Litvinov et al., Nucl. Phys. A 756 3 (2005)

13. First claimed new isomer. B.Sun et al., Eur. Phys. J. A 31 393 (2007)

14. 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 188 Hf (compares with K=16, 31-year isomer in 178 Hf). Search for this isomer is ongoing. Other new isomers have been identified.

15. New Isomer from current data set Compare: 1.3MeV isomer in 215 Bi, I=(25/2-) T 1/2 =36.4 s L.Chen to be published

16. Conclusions ESR experiment sensitive to isomers with T 1/2 > 1s. Isomers with energy ~100keV can be resolved. Current analysis is ongoing and hopes are high of finding previously unobserved isomers.

17. Collaborators I.J.Cullen 1, P.M. Walker 1, Z. Liu 1, Yu.A. Litvinov 2, L. Chen 2,3, K. Beckert 2, P.Beller 2, F. Bosch 2, D. Boutin 2,3, L. Caceres 1, R.S. Chakrawarthy 4, D. Cullen 5, B. Franzke 2, H.-Geissel 2,3, J. Gerl 2, E. Greda 2, G. Jones 1, A. Kishada 5, O. Klepper 2, H.-J. Kluge 2, R. Knöbel 2,3, C. Kozhuharov 2, E. Kulich 2, N. Kuziminchuk 2, S.A. Litvinov 2,3, S. Mandal 2, M. Matoš 6, M. Montes 6, G. Münzenberg 2, F. Nolden 2, Yu.N. Novikov 7, W.R. Plass 3, Zs. Podolyak 1, R. Propri 8, S. Rigby 5, N. Saito 2, T. Saito 2, C. Scheidenberger 2, M. Shindo 9, M. Steck 2, P. Ugorowski 8, G. Vorobjev 2, H. Weick 2, S. Williams 1, M. Winkler 2, H.-J. Wollersheim 2. 1 Surrey University, 2 GSI, 3 JLU Giessen, 4 TRIUMF Vancouver, 5 Manchester University, 6 MSU East Lansing, 7 PNPI Gatchina, 8 SU Youngstown, 9 Tokyo University