Properties ofγ-Ray Transitions inCo56fromNi56Decay andFe56(p, nγ)Co56

The ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ $\epsilon$ decay and the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ reaction with beam energies between 5.5 and 8.4 MeV have been used with Ge(Li) spectrometers to study the properties of $\gamma$ rays from states of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ below 2.86 MeV excitation. From ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ $\epsilon$ decay both the $\gamma$-ray spectrum and $\gamma -\gamma$ coincidences were studied. $\gamma -\gamma$ coincidences, $\gamma$-ray excitation functions, $\gamma$-ray angular distributions, and absolute cross sections were measured for the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ reaction. An $\epsilon$ decay scheme for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$, which includes six $\gamma$ rays, and an energy-level diagram for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$, which includes 35 $\gamma$ rays (14 of which are reported for the first time) from 20 excited states, are presented. Comparison of the data from ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(p, n\gamma ){}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ with predictions of the statistical compound-nuclear model have resulted in spin assignments (in parentheses) for the following states (energies in keV) of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$: 158.4(3), 576.6(5), 829.7(4), 970.3(2), 1009.2(5), 1114.6(3), 1450.8(0), and 1720.3(1). Branching ratios are presented for 14 $\gamma$ rays from these eight states and multipole mixing ratios are given for 12 of these $\gamma$ rays (10 are predominantly $M1\mathrm{}$). The data are consistent with a spin-4 assignment to the ground state. Contrary to previous suggestions, evidence from all experiments indicates that only one state (believed to be the antianalog of the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ ground state) exists in ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ in the neighborhood of 1451 keV excitation. The level energies, $\gamma$-ray multipole mixing ratios, and $\gamma$-ray branching ratios agree, in general, with shell-model predictions of McGrory.