Shell model calculations for levels and transition rates in 204Pb and 206Pb.

Abstract

Level energies and decay rates of both negative and positive parity levels of $^{206,204}\mathrm{Pb}$ have been calculated through mixed-configuration shell model calculations using the modified surface delta interaction (MSDI), the Schiffer-True central interaction, and another two-body interaction. These calculations were all carried out with a full six-orbit neutron hole space. The predicted low-lying levels with the MSDI are in excellent agreement with experiments, accounting for the energies, spins, and parities of essentially all levels below 3 MeV excitation energy except known particle-hole collective excitations in both nuclei. Almost all calculated $E2$ and $M1$ transition rates are consistent with measured branching ratios for $\ensuremath{\gamma}$-ray decay of excited levels. The comparison of the observed and calculated levels demonstrates the important role played by the neutron-hole ${i}_{\frac{13}{2}}$ configuration in the levels of $^{204}\mathrm{Pb}$ and $^{206}\mathrm{Pb}$, and interprets an apparent discrepancy over the character and energy spacings of ${0}^{+}$ levels in $^{204}\mathrm{Pb}$.