PnQRPA calculation of the β+/EC quenching for several neutron-deficient nuclei in mass regions A = 94–110 and A =146–156★

Abstract

Abstract We apply the proton-neutron quasi-particle random-phase approximation (pnQRPA) to 22 neutron-deficient spherical nuclei in the mass regions A = 94–110 and f = 146–156. The pnQRPA contains two important parameters: the particle-hole interaction strength g ph , which influences the energy of the Gamow-Teller giant resonance (GTGR), and the particle-particle interaction strength g pp which causes the quenching of the Gamow-Teller β + /EC transition strength, B (GT) + , through proton-neutron correlations in the decaying parent nucleus. For a realistic interaction like the reaction matrix of the Bonn potential both parameters are given by g ph = g pp =1. We used a semi-empirical energy formula for the GTGR to determine the value of g ph , resulting in g ph = 1.0 for the lighter mass region and in g ph = 1.3 for the heavier one. Some of the nuclei were used to build up a g pp -value systematics from the available log ft data. In this systematics the g pp values lie close to unity. For the rest of the nuclei we predict quenched B (GT) + and log ft values and give the decay half-life t + 1/2 as a function of the β + decay Q -value. The doubly magic 100 Sn is also discussed as a limiting case of the pnQRPA.