High-spin microsecond isomers in129Inand129Sb

Abstract

In this work the microsecond isomers in ${}^{129}\mathrm{In}$ and ${}^{129}\mathrm{Sb}$ were investigated. These nuclei were produced by the thermal-neutron-induced fission of ${}^{241}\mathrm{Pu}.$ The detection is based on a time correlation between the fission fragments selected by the LOHENGRIN spectrometer at the ILL (Grenoble) and the $\ensuremath{\gamma}$ rays or conversion electrons from the isomers. The decay schemes of the new ${17/2}^{\ensuremath{-}}$ isomer in ${}^{129}\mathrm{In}$ and ${23/2}^{+}$ isomer in ${}^{129}\mathrm{Sb}$ are reported. A shell-model study of these two nuclei was performed using a realistic effective interaction derived from the CD--Bonn nucleon-nucleon potential. Comparison shows that the calculated energy levels and electromagnetic transition rates are in very good agreement with the experimental data.