Spin-trap isomers in deformed, odd-odd nuclei in the light rare-earth region near N=98

Abstract

Masses of neutron-rich, odd-odd Pm, Eu, and Tb nuclei near $N=98$ were measured using the Canadian Penning Trap mass spectrometer at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility. High-resolution mass measurements yielded the discovery of spin-trap isomers at $N=97$ in $^{162}\mathrm{Tb}$, and in the $N=99$ isotones of $^{160}\mathrm{Pm}$ and $^{164}\mathrm{Tb}$. Furthermore, no evidence of long-lived isomers were observed at $N=95$ in $^{158}\mathrm{Eu}$, at $N=97$ in $^{158}\mathrm{Pm}$, nor at $N=101$ in $^{164}\mathrm{Eu}$ and $^{166}\mathrm{Tb}$. These experimental observations are compared to results from multiquasiparticle blocking calculations.