Isomeric states of fission fragments explored via Penning trap mass spectrometry at IGISOL

Abstract

The masses of ${}^{84}$Br, ${}^{105}$Mo, ${}^{115,119,121}$Pd, ${}^{122}$Ag, ${}^{127,129}$In, ${}^{132}$Sb and their respective isomeric states have been measured with the JYFLTRAP Penning trap mass spectrometer using the phase-imaging ion-cyclotron-resonance technique. The excitation energies of the isomeric states in ${}^{132}$Sb and ${}^{119}$Pd were experimentally determined for the first time, while for ${}^{84}$Br, ${}^{115}$Pd and ${}^{127,129}$In, the precision of the mass values was substantially improved. In ${}^{105}$Mo and ${}^{121}$Pd there were no signs of a long-lived isomeric state. The ground-state measurements of ${}^{119}$Pd and ${}^{122}$Ag indicated that both are significantly more bound than the literature values. For ${}^{122}$Ag, there was no indication of a proposed third long-lived state. The results for the $N=49$ nucleus ${}^{84}$Br and isomers close to doubly magic ${}^{132}$Sn have been compared to the shell-model and the microscopic quasiparticle-phonon model calculations.

14 pages, 10 figures