Quadrupole Interaction and High-Spin States in the Lead Region

The energies of high-spin states formed by adding a few valence nucleons to ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ can be accurately calculated by using empirical interaction matrix elements. It is shown that the energies of high-spin states with ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$, and ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$ as the core can also be accurately calculated if an additional quadrupole interaction with a strength proportional to the increased polarizability of the core is included. This interaction may contribute to the formation of yrast traps from states with a few valence nucleons with aligned angular momenta.