Levels inGd154populated by the (α, 2nγ) reaction and the decay of the isomers ofTb154

Abstract

Levels in $^{154}\mathrm{Gd}$ have been studied using the $^{152}\mathrm{Sm}(\ensuremath{\alpha}, 2n\ensuremath{\gamma})$ reaction at an energy of 24 MeV. Singles spectra, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence spectra, and angular distributions were obtained in-beam using Ge(Li) detectors. Among the new levels proposed in $^{154}\mathrm{Gd}$ are as follows: a ${7}^{+}$ state in the $\ensuremath{\gamma}$ band; ${7}^{\ensuremath{-}}$, ${9}^{\ensuremath{-}}$, and ${11}^{\ensuremath{-}}$ states in an odd-spin octupole-vibrational band based at 1241 keV; possible ${7}^{+}$ and ${8}^{+}$ states in the ${K}^{\ensuremath{\pi}}={4}^{+}$ band based at 1646 keV; and ${8}^{\ensuremath{-}}$ and ${9}^{\ensuremath{-}}$ members of a $K=7$ band based on the ${7}^{\ensuremath{-}}$ state at 2138 keV. The results are compared with various theoretical models. $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ directional correlation measurements were also performed on some cascades populated in the radioactive decay of the various isomers of $^{154}\mathrm{Tb}$, and the results confirm the assignment of ${7}^{\ensuremath{-}}$ for the 2137.8 keV state and establish a spin value of 1 for the 2119.7 and 2187.2 keV states.NUCLEAR REACTIONS $^{152}\mathrm{Sm}(\ensuremath{\alpha}, 2n\ensuremath{\gamma})$, $E=24$ MeV, measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}\ensuremath{\gamma}$ (delay), $\ensuremath{\gamma}\ensuremath{\gamma}$ coin, $\ensuremath{\gamma}(\ensuremath{\theta})$ $^{154}\mathrm{Gd}$ deduced levels, $K$, $J$, $\ensuremath{\pi}$, $\ensuremath{\delta}$, $Q$. Enriched targets. Ge(Li) detectors. RADIOACTIVITY $^{154}\mathrm{Tb}$(22.6, 9.0, and 21.4 h) from $^{153}\mathrm{Eu}(\ensuremath{\alpha}, 3n)$ and $^{155}\mathrm{Gd}(p, 2n)$. Measured $\ensuremath{\gamma}\ensuremath{\gamma}(\ensuremath{\theta})$ $^{154}\mathrm{Gd}$ deduced $J$, $\ensuremath{\pi}$, $\ensuremath{\delta}$. Enriched targets. Ge(Li) detectors.