Excited Levels inMn56

Abstract

The half-lives of the first three excited levels of ${\mathrm{Mn}}^{56}$ have been measured by looking at the cascade gamma rays from neutron capture in ${\mathrm{Mn}}^{55}$. They are found to be ${10.7}_{-3\mathrm{}}^{+2\mathrm{}}$ mμsec, 4.9±0.6 mμsec, and ≤0.5 mμsec. A fairly plausible assignment of spins and parities to the first, second, and third excited levels of ${\mathrm{Mn}}^{56}$ would seem to be $2^{+}$, $1^{+}$, and $2^{+}$, respectively. The technique described in the paper should be useful in those cases in which excited levels of unstable nuclei cannot be reached through beta decay.