Identification ofTb145andTb144and levels in theN=81nucleus,Gd145

With the use of a helium gas-jet transport system the isotopes ${}_{}{}^{145}{}_{}{}^{}\mathrm{Tb}$ and ${}_{}{}^{144}{}_{}{}^{}\mathrm{Tb}$ were identified in a series of ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$+${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ irradiations. Nuclidic assignments were based on yields as a function of bombarding energy, $\gamma$-ray coincidences with gadolinium $K$ x rays, and comparisons with data from in-beam $\gamma$-ray studies. Thirteen transitions were observed to follow the decay of ${}_{}{}^{145}{}_{}{}^{}\mathrm{Tb}$ ($T_{\frac{1}{2}}=30\mathrm{}\pm 3$ sec). Nine of them were placed in a scheme incorporating six excited levels in ${}_{}{}^{145}{}_{}{}^{}\mathrm{Gd}$, the lowest two of which, 27.3 and 748.7 keV, were previously known from ${}_{}{}^{145}{}_{}{}^{}\mathrm{Gd}_{}^m{}_{}{}^{}$ decay. The nuclide ${}_{}{}^{144}{}_{}{}^{}\mathrm{Tb}$ ($T_{\frac{1}{2}}=5\mathrm{}\pm 1$ sec) was identified by observing the 742.9-keV $\gamma$ ray known from in-beam studies to be the $2^{+}$ (first-excited state)→$0^{+}$ (ground state) transition in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Gd}$.