Short-Lived Isomers ofTb148andTb147

A 2.5-min activity previously assigned to ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$ is shown to be 2.20 ± 0.05-min ${}_{}{}^{148}{}_{}{}^{}\mathrm{Tb}$. Levels are proposed in ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$ at 784.48, 1273.31, 1416.35, 1754.96, 1810.90, 2563.8, and 2693.31 keV. The decay of this ${}_{}{}^{148}{}_{}{}^{}\mathrm{Tb}$ activity occurs almost entirely to a single high-lying, high-spin level in ${}_{}{}^{148}{}_{}{}^{}\mathrm{Gd}$. A short-lived ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$ isomer is found to have a half-life of 1.83 ± 0.06 min and prominent $\gamma$ rays of energy 1397.3 and 1798.0 keV.