Shell-model calculation for two-neutrino double beta decay of Ca48
The 2 decay matrix element of Ca48 has been studied in a large basis shell-model space. The theoretical and experimental - and + spectra and their relation to 21/2 are discussed. A new empirical effective interaction is found to give the best agreement to - and + spectra with the effective Gamow-Teller operator Ìt=0.77t. The predicted T1/2=1.9×1019 yr differs by a factor of 2 from the present experimental limit of T1/2>3.6×1019 yr. We also compare the matrix elements obtained at various levels of the truncation in the shell-model space. © 1990 The American Physical Society.