Abstract :
Two-neutrino double-beta decay half-lives for the transitions to the first excited 2+ and 0+ states have been computed in the framework of a second quasi random phase aproximation (QRPA) in the cases of 100Mo and 96Zr. In addition, other single-beta decay rates and B(E2) transitions related to the same nuclei are evaluated and compared with experimental data. We have found a good agreement between theory and experiment for all the computed quantities except the B(E2) transitions in 100Mo and 100Ru. For the ββ decay transitions studied we predict half-lives of the order of 1021–1022 yr.