Isomerism inTb147

Abstract

The previous assignment of a 24-min activity to ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$ was found to be in error. Two ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$ isomers with half-lives of 1.61±0.17 h and 2.5±0.1 min were found and their $\gamma$-ray spectra determined. The 1.6-h isomer appears to be the ground state, with spin-parity ${\frac{5}{2}}^{-}$; the 2.5-min ${}_{}{}^{147m}{}_{}{}^{}\mathrm{Tb}$ is the high-spin state ($\ge \frac{11}{2}$). The half-life and prominent $\gamma$ rays of ${}_{}{}^{147}{}_{}{}^{}\mathrm{Gd}$ were redetermined and two new $\gamma$ rays associated with the decay of 4.3-min ${}_{}{}^{149m}{}_{}{}^{}\mathrm{Tb}$ are reported.