Level Structure inCr52Populated in 5.7-DayMn52Decay

Abstract

The energy-level structure in ${\mathrm{Cr}}^{52}$ populated in the decay of 5.7-day ${\mathrm{Mn}}^{52}$ has been studied with a toroidalfield electron spectrometer and Ge(Li) detector. The decay is found to populate only the states at (MeV, $J_{\pi }$, $v=\mathrm{dominant}\mathrm{seniority}$) (3.6177, 5+, 4), (3.1146, 6+ 2), (2.7688, 4+, 2), (2.3703, 4+, 4), and (1.4345, 2+, 2). Low upper limits set on the intensity of gamma rays of 2.65, 1.73, 1.465, 1.214, 1.18, 1.07, and 0.61 MeV previously reported in ${\mathrm{Mn}}^{52}$ remove all evidence for the population by ${\mathrm{Mn}}^{52}$ of states at 3.832, 3.161, and 2.648 MeV (the latter two known from nuclear reactions). All 9 possible transitions of multipolarity $E2\mathrm{}$ or lower between known levels have been seen, including new weak gammas of 0.504 and 0.398 MeV. Conversion coefficients indicate strong $M1\mathrm{}$ mixing only in the transition of 1.2474 MeV from the 3.6177- to the 2.7686-Mev state, for which $\Delta v=0\mathrm{}$, in agreement with seniority selection rule for half-filled shells; and $E2\mathrm{}$ dominance in the 1.4345-, 1.3343-, 0.9358-, 0.8498-, 0.7443-, and 0.3460-MeV transitions. Seniority mixing coefficients in the two 4+ states deduced from gamma intensities agree with those derived from previously reported nuclear-reaction data. The ratio of electron capture to positron emission for decay to the 6+ state is 2.04, in good agreement with theory.