Competition between α and β decays for heavy deformed neutron-deficient Pa, U, Np, and Pu isotopes

Abstract

The competition between $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ decays is investigated for neutron-deficient Pa, U, Np, and Pu isotopes. ${\ensuremath{\beta}}^{+}$/electron-capture (EC) decay rates are calculated within the deformed quasiparticle random-phase approximation with realistic nucleon-nucleon $(NN)$ interactions. Contributions from allowed Gamow-Teller and Fermi transitions as well as first-forbidden transitions are considered. $\ensuremath{\alpha}$-decay calculations are performed within the generalized density-dependent cluster model. Effects of differences between neutron and proton distributions and nuclear deformation are taken into account. In the calculations, Reid-93 $NN$ interactions are used for ${\ensuremath{\beta}}^{+}/\mathrm{EC}$ decays, while Michigan three-range Yukawa effective interactions, based on the $G$-matrix elements of Reid $NN$ potentials, are used for $\ensuremath{\alpha}$ decay. The calculated $\ensuremath{\beta}$-decay half-lives show good agreement with the experimental data over a range of magnitude from ${10}^{2}$ to ${10}^{5}$ s. The resulting total half-lives including $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ contributions are found to be in good agreement with the experimental data, together with the $\ensuremath{\alpha}/\ensuremath{\beta}$-decay branching ratios.