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 
-decay of isomeric levels
in 187Tl has been
studied using delayed -
coincidence measurements. From
observation of their subsequent
decay, the mean lifetimes were
measured to be 
ns and
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 
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
Copyright Società Italiana di Fisica, Springer-Verlag 2000
