We have measured with high accuracy the $\gamma$ rays from 66-sec ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$, 1.6-min ${}_{}{}^{57}{}_{}{}^{}\mathrm{Mn}$, and 2.6-h ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$. Thirty-seven $\gamma$ rays were observed from ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$ decay which were incorporated into a ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$ level scheme with 17 excited states below 4.9 MeV. Present evidence favors a $3^{+}$ assignment for the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$ ground state, but the $\beta$ decays to low-lying $2^{+}$ states are hindered. Additional weak $\gamma$ transitions giving rise to new $\beta$-decay modes were observed from ${}_{}{}^{57}{}_{}{}^{}\mathrm{Mn}$ and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$ decays.

RADIOACTIVITY ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Mn}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$; measured $E_{\gamma }$, $I_{\gamma }$. ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ deduced levels, $log\mathrm{ft}$, $J^{\pi }$. Enriched targets, Ge(Li) detector.

• Received 3 April 1974

DOI:https://doi.org/10.1103/PhysRevC.10.785