Microscopic investigation of the $I^{\pi }=8^{-}$ isomer decay in even-even N = 74 isotones

Abstract

The microscopic approach of the triaxial projected shell model (TPSM) is employed to investigate the properties of the $8^{-}$ isomer in the six isotones of ${}^{128}$Xe, ${}^{130}$Ba, ${}^{132}$Ce, ${}^{134}$Nd, ${}^{136}$Sm, and ${}^{138}$Gd. The observed decay pattern of the isomer for these isotones is unexpected with the hindrance factor decreasing with atomic number. It is shown in the present work that multi-quasiparticle mixing into the ground-state configuration is responsible for the observed decreasing trend of the hindrance factor. We have also calculated the excitation energies and in-band $B(E2)$ transition probabilities of the yrast and the band built on the $8^{-}$ isomer for the six isotones, and it is shown that TPSM approach reproduces the measured quantities quite satisfactorily.

Comments: 11 pages, 8 figures