The study of nuclei which are one neutron removed from the $N=126\mathrm{}$ closed shell has shown that the odd-proton $N=127\mathrm{}$ isotones $\alpha$ decay from both the ground state and a metastable state whose excitation energy decreases between ${}_{}{}^{210}{}_{}{}^{}\mathrm{Bi}$ and ${}_{}{}^{216}{}_{}{}^{}\mathrm{Ac}$. The $\alpha$-decay daughters of these nuclei show some correspondence in their energy-level spacings which is due to the coupling of specific single-particle configurations near the $N=126\mathrm{}$ closed shell. New information has been obtained for the $\alpha$ decay of the 1 - isomer of ${}_{}{}^{214}{}_{}{}^{}\mathrm{Fr}$ to levels in ${}_{}{}^{210}{}_{}{}^{}\mathrm{At}$, and for the $\alpha$ decay of ${}_{}{}^{216}{}_{}{}^{}\mathrm{Ac}$ to levels in ${}_{}{}^{212}{}_{}{}^{}\mathrm{Fr}$. The decay scheme of ${}_{}{}^{216}{}_{}{}^{}\mathrm{Ac}$ is markedly different from that reported by others. An experimental and theoretical study of the $\alpha$ decay of ${}_{}{}^{215}{}_{}{}^{}\mathrm{Ra}$ has also been made.

• Received 11 August 1970

DOI:https://doi.org/10.1103/PhysRevC.2.2309