A 9.5-s activity with an isomeric transition of unusually low energy (3.2 keV) and a subsequent transition of 56.5 keV has been assigned to ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ga}_{}^m{}_{}{}^{}$. The activity has been produced by 14-MeV neutrons in samples of ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}$. Since this target nucleus has an abundance of 37% in natural germanium, summing of the 3.2- and 56.5-keV transitions could be observed by neutron activation of a Ge detector. Further experiments utilized fast transport and analysis of x rays, $\beta$ rays, and sum peaks. Combining the results with recent information on the decay of ${}_{}{}^{74}{}_{}{}^{}\mathrm{Zn}$, spins and parities could be proposed for levels of ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ga}$ at 56.5, 59.7, 108.6, and 250.0 keV. For the ground state we propose $J^{\pi }=4^{-}$, which is in contrast with previous suggestions of $3^{-}$ based on analogy to the neighbouring isotopes ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ga}$ and ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ga}$.

[RADIOACTIVITY ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ga}_{}^m{}_{}{}^{}$; assignment, measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $\frac{{\sigma }_m}{{\sigma }_g}$, x rays. Sum peak in an activated Ge detector. Deduced levels, $J$, $\pi$. Calculated $\mathrm{jj}$ coupling.]

• Received 5 October 1973

DOI:https://doi.org/10.1103/PhysRevC.9.2252