β decay and evolution of low-lying structure in Ge and As nuclei

A simultaneous calculation for the shape evolution and the related spectroscopic properties of the low-lying states, and the beta-decay properties in the even- and odd-mass Ge and As nuclei in the mass A approximate to 70-80 region, within the framework of the nuclear density functional theory and the particle-core coupling scheme, is presented. The constrained self-consistent mean-field calculations using a universal energy density functional (EDF) and a pairing interaction determines the interacting-boson Hamiltonian for the even-even core nuclei, and the essential ingredients of the particle-boson interactions for the odd-nucleon systems, and of the Gamow-Teller and Fermi transition operators. A rapid structural evolution from gamma-soft oblate to prolate shapes, as well as the spherical-oblate shape coexistence around the neutron subshell closure N = 40, is suggested to occur in the even-even Ge nuclei. The predicted low-energy spectra, electromagnetic transition rates, and beta-decay log ft values are in a reasonable agreement with experiment. The predicted log ft values reflect the structures of the wave functions for the initial and final nuclei of beta decay, which are, to a large extent, determined by the microscopic input provided by the underlying EDF calculation.