Energy Levels inNp235

Abstract

The energy levels in ${}_{}{}^{235}{}_{}{}^{}\mathrm{Np}$ have been studied through the $\alpha$ decay of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Am}$ and the electron-capture decay of ${}_{}{}^{235}{}_{}{}^{}\mathrm{Pu}$. A level was observed at 34.1 keV and assigned to the ground-state rotational band with Nilsson quantum numbers $\frac{5}{2}+\left[642\right]\mathrm{}$. Levels at 49.0, 91.6, and 146.8 keV were assigned to the $\frac{5}{2}-\left[523\right]\mathrm{}$ rotational band. The lifetime of the 49.0-keV state was measured as 6.9 nsec, and the half-life of the ${}_{}{}^{235}{}_{}{}^{}\mathrm{Pu}$ was redetermined to be 24.3 min.