Shell Model andPb208

Abstract

The lowest odd-parity excited energy levels of ${\mathrm{Pb}}^{208}$ have been calculated by a shell-model approach considering a single proton or a single neutron to be excited out of the ${\mathrm{Pb}}^{208}$ core. Both a singlet-even plus triplet-even force and a Rosenfeld force were used as the two-particle interaction. A zero-range force was also considered. There were no other arbitrary parameters. The results with the various forces indicate that it is impossible to get a 3- state low enough to be interpretated as the observed 2.615-Mev 3- level. The results, therefore, support the conclusion that the 3- level at 2.615 Mev in ${\mathrm{Pb}}^{208}$ is primarily the result of a collective octupole oscillation.