We have observed isomeric states in ${}_{}{}^{212}{}_{}{}^{}\mathrm{Rn}$ with very high angular momenta (up to $J^{\pi }={30}^{+}$). The four isomers of highest spin contain core-excited neutron configurations, the spins of which are strongly aligned with those of the valence protons. The isomerism appears to result from a lowering of the excitation energies by 1 to 2 MeV compared to a sum of the unperturbed values for the constituent configurations.

• Received 20 June 1977

DOI:https://doi.org/10.1103/PhysRevLett.39.389