2019 Impact factor 2.176
Hadrons and Nuclei
Eur. Phys. J. A 7, 41-44

Microsecond isomers in 187Tl and 188Pb

A.P. Byrne1 - A.M. Baxter1 - G.D. Dracoulis2 - S.M. Mullins2 - T. Kibédi2 - T.R. McGoram2 - K. Helariutta3 - J.F.C. Cocks3 - P. Jones3 - R. Julin3 - S. Juutinen3 - H. Kankaanpää3 - H. Kettunen3 - P. Kuusiniemi3 - M. Leino3 - M. Muikku3 - P. Nieminen3 - P. Rahkila3 - A. Savelius3

1 Department of Physics and Theoretical Physics, Faculty of Science, Australian National University, Canberra 0200,
Australia
2 Department of Nuclear Physics, RSPhysSE, Australian National University, Canberra 0200, Australia
3 Department of Physics, University of Jyväskylä, P.O. Box 35, 40351 Jyväskylä, Finland

Received: 20 August 1999 Communicated by B. Herskind

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 $\gamma$-decay of isomeric levels in 187Tl has been studied using delayed $\gamma$-$\gamma$ coincidence measurements. From observation of their subsequent $\gamma$ decay, the mean lifetimes were measured to be $1000\pm55$ ns and $1600\pm100$ 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 $1150\pm30$ ns, and limits of 20-600 ns were placed on the meanlife of an isomer conjectured in 187Pb.

PACS
21.10.Re Collective levels - 23.20.Lv Gamma transitions and level energies - 27.70.+q
$150 \leq A \leq 189$


Copyright Società Italiana di Fisica, Springer-Verlag 2000