Systematic study of the single-state dominance in 2νββ decay transitions Original Research Article

The single-state-dominance hypothesis (SSDH) states that the decay rates of the two-neutrino double-beta decay are governed by a virtual two-step transition connecting the initial and final ground states through the first 1+ state, 1l+, of the intermediate odd-odd nucleus, for those odd-odd nuclei where the 1l+ state is the ground state. To investigate the validity of the SSDH we have performed a systematical theoretical analysis of all known double-beta-decay transitions where the SSDH conditions are fulfilled. the calculations are based on the quasiparticle random-phase approximation (QRPA) and the results have been obtained by using realistic single-particle bases and realistic interactions. We have studied the double β− decays of 100Mo, 110Pd, 114Cd, 116Cd and 128Te and the double electron-capture transitions in 106Cd and 136Ce. The analysis shows that the SSDH is realized either through a true dominance of the first intermediate 1+ state or by cancellations among the contributions of higher lying 1+ states of the intermediate nucleus.