Coupling of Angular Momenta in Two-Particle States in Deformed Even-Even Nuclei

Abstract

The recent suggestion that low-lying intrinsic states in deformed nuclei are basically two-particle excitations is considered in more detail. The result of the strong-coupling model that the two-particle states are doubly degenerate with spins $\ensuremath{\Omega}=|{\ensuremath{\Omega}}_{1}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\Omega}}_{2}|$ is re-emphasized. It is suggested on the basis of experimental evidence that the degeneracy of the two states of each configuration is removed largely by residual spin-dependent forces, analogous to the splitting observed in deformed odd-odd nuclei. Coupling rules are given for the lower-lying state of each configuration based on this assumption. As an example of the application of the coupling rules to actual nuclei the decay schemes of the two ${\mathrm{Ta}}^{178}$ isomers to levels in ${\mathrm{Hf}}^{178}$ are considered in detail.