Systematic approach to β and 2vββ decays of mass A=100-136 nuclei

In this work we perform a systematic study of pairs of single-β-decaying nuclei in the mass region A = 100–136 to extract information on the effective value of the axial-vector coupling constant gA. As the many-body framework we use the quasiparticle random-phase approximation (QRPA) and its proton-neutron variant (pnQRPA) in singleparticle valence bases with Woods-Saxon-calculated single-particle energies. It is found that, to a reasonable approximation, gA is a linear function of the mass number A, with a slightly different parametrization below and above the mass A = 121. Using the values of gA extracted from the linear fit, as well as an average constant value of gA, we calculate the two-neutrino double-β (2νββ) decay half-lives of 11 β−β− decays and 10 mixed β+ and electron-capture (EC) decays, β+β+/β+EC/ECEC, to both the ground state and the lowest three excited states.peerReviewe