Predicted features of the beta decay of neutron-rich sd-shell nuclei

The Gamow-Teller beta-decay transitions of sd-shell nuclei with five or more excess neutrons are calculated from complete (0d/sub 5/2/, 1s/sub 1/2/, 0d/sub 3/2/)-space shell-model wave functions. These wave functions are obtained from diagonalizations of a model Hamiltonian formulation which reproduces observed energy-level structures throughout the sd shell. The calculations are carried out with both the ''free-nucleon'' normalization for the Gamow-Teller single-nucleon matrix elements and one based on the empirical values obtained for these quantities from a comparison of corresponding theoretical and experimental Gamow-Teller magnitudes near the line of stability. The phase-space factors f which connect the reduced Gamow-Teller strengths to the total half-lives and the individual decay probabilities are calculated both from the energies obtained in the shell-model calculations and, alternatively, from hybrid energy spectra in which available experimental energies are substituted for the corresponding calculated values wherever possible. Comparisons of the beta-decay predictions to existing experimental results are presented and discussed