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Microsecond isomers in 187Tl and 188Pb |
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| Authors: | A.P. Byrne A.M. Baxter G.D. Dracoulis S.M. Mullins T. Kibédi T.R. McGoram K. Helariutta J.F.C. Cocks P. Jones R. Julin S. Juutinen H. Kankaanpää H. Kettunen P. Kuusiniemi M. Leino M. Muikku P. Nieminen P. Rahkila A. Savelius |
| Affiliation: | Department of Physics and Theoretical Physics, Faculty of Science, Australian National University, Canberra 0200, Australia, AU Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra 0200, Australia, AU Department of Physics, University of Jyv?skyl?, P.O. Box 35, 40351 Jyv?skyl?, Finland, FI |
| Abstract: | Lifetime measurements of states in nuclei with A=187 and 188 have been performed, using reactions between 155Gd and 36Ar and following the transport of evaporation residues to the focal plane of a gas-filled recoil separator. In a separate experiment using the 159Tb(32S, 4n) reaction the γ-decay of isomeric levels in 187Tl has been studied using delayed γ-γ coincidence measurements. From observation of their subsequent γ decay, the mean lifetimes were measured to be 1000 ± 55 ns and 1600 ± 100 ns. Although it was not possible to characterize the isomers completely, they are proposed as candidates for one-proton, two-neutron excitations. In the course of this study, the decay of an isomer in 188Pb was also observed and its lifetime was measured as 1150 ± 30 ns, and limits of 20–600 ns were placed on the meanlife of an isomer conjectured in 187Pb. Received: 20 August 1999 |
| Keywords: | PACS: 21.10.Re Collective levels – 23.20.Lv Gamma transitions and level energies – 27.70.+q 150 ≤ A ≤ 189 |
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