A 62.0±0.4-sec isomer, ${\mathrm{Sc}}^{42m}$, has been observed which decays by emission of a positron group of endpoint energy 2.87±0.10 MeV to an excited state in ${\mathrm{Ca}}^{42}$ at 3.191 MeV, followed by a cascade of three $\gamma$ rays of energies 0.438±0.003, 1.226±0.010, and 1.520±0.010 MeV. The levels of ${\mathrm{Ca}}^{42}$ and their assigned spins are: 1.523 MeV, 2+; 1.836 MeV, 0+; 2.424 MeV, 2+(1+); 2.750 MeV, 4+; and 3.191 MeV, 6+. The spin of ${\mathrm{Sc}}^{42m}$ is 7+. Studies of the reaction ${\mathrm{Ca}}^{40}({\mathrm{He}}^3,p)$ showed that the first and second excited states of ${\mathrm{Sc}}^{42}$ are at 0.67±0.03 and 1.58±0.05 MeV, respectively, the former being ${\mathrm{Sc}}^{42m}$. The excitation function for the ${\mathrm{Ca}}^{40}(\alpha ,pn){\mathrm{Sc}}^{42m}$ reaction was also measured. The general trends of levels in even $f_{\frac{7}{2}}$ nuclides are rather well explained by two treatments of the $\mathrm{jj}$-coupling model, with exceptions for ${\mathrm{Ca}}^{44}$ and ${\mathrm{Ca}}^{42}$.

• Received 2 November 1962

DOI:https://doi.org/10.1103/PhysRev.129.2653