Overlap of electron shells in β and double-β decays
Abstract
The β and double-β decay channels, which are not accompanied by excitation of the electron shells, are suppressed due to the nonorthogonality of the electron wave functions of the parent and daughter atoms. The effect is sensitive to the contribution of the outer electron shells. Since valence electrons participate in chemical bonding and collectivize in metals, the decay rates of the unstable nuclides are modified when they are embedded in a host material. Core electrons are less affected by the environment, and their overlap amplitudes are more stable. The suppression effect is estimated for β- decay of 87Kr, electron capture in 163Ho, and 2β- decays of 76Ge, 100Mo, 130Te, and 136Xe. The overlap amplitude of the electron shells enters the relationship between the half-life of neutrinoless 2β decay and the effective electron neutrino Majorana mass.