New half-life measurements of the most neutron-rich arsenic and germanium isotopes

The β-decay properties of several neutron-rich germanium and arsenic isotopes were measured at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The measurements of almost-pure radioactive sources were enabled by the combination of ion-source chemistry and two-stage mass separation. The half-life of 86Ge (226±21 ms) was determined for the first time, while those of 84^,85Ge and 84^-87As were remeasured. The results are compared to theoretical predictions of the gross theory of β decay, the finite-range droplet model, and the new calculations using the energy density functional DF3a with continuum quasiparticle random-phase approximation (CQRPA). We confirm the robustness and good predictive power of the latter model for nuclei near closed shells. These DF3a+CQRPA calculations were used recently to analyze r-process isobaric abundances.