BETA+ GAMOW-TELLER STRENGTH IN NUCLEI

The distribution of beta+ Gamow-Teller strength in Mg-26, Fe-54 and Ni-56 is calculated in the QRPA and large-basis shell-model spaces. The quenching relative to the simplest jj coupled model found in the QRPA is similar to that found in a shell-model basis which includes 2p2h ground-state correlations within the major shell (sd or pf). For Mg-26 there is significant additional quenching found in the full sd shell-model space relative to the 2p2h model space. We explore the connection between this additional quenching and the transition from jj to SU (3) LS coupling via its relationship to the quadrupole collectivity. From this analysis we are able to estimate the total beta+ strength in Fe-54 and and Ni-56 which would be obtained in the full pf shell-model space. These calculations, together with the global quenching factor of 0.6, account for the observed strength in these nuclei. The quenching effects appearing in heavier nuclei are discussed.