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

Abstract

The $\ensuremath{\beta}$-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 ${}^{86}$Ge ($226\ifmmode\pm\else\textpm\fi{}21$ ms) was determined for the first time, while those of ${}^{84,85}$Ge and ${}^{84\ensuremath{-}87}$As were remeasured. The results are compared to theoretical predictions of the gross theory of $\ensuremath{\beta}$ 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.