β-decay rates of r-process waiting-point nuclei in the extended quasiparticle random-phase approximation

The β− decays of the r-process waiting-point nuclei at the neutron magic numbers N = 50 and N = 82 are investigated within the extended quasiparticle random-phase approximation (QRPA), where neutron–neutron, proton–proton and neutron–proton (np) pairing correlations are considered in the specialized Hartree–Fock–Bogoliubov (HFB) calculation. The Brückner G-matrix obtained with the charge-dependent Bonn nucleon–nucleon force is used for the residual particle–particle and particle–hole interaction in addition to the pairing interaction. It is found that the np pairing interaction plays an important role in reducing the calculated β−-decay half-lives. The calculations with np pairing show good agreement with the available experimental data including the decay half-lives of Ni isotopes, which are usually overestimated in the self-consistent proton–neutron QRPA calculations. (paper)