A survey of experimental data about transitions between low-lying nuclear states shows that the great majority of transitions in nuclei with is severely inhibited. For heavy nuclei with a permanent deformation, the inhibition can be ascribed either to forbiddenness or to an asymptotic selection rule. Even when a permanent deformation is not present, the effect of this selection rule may persist, and it can lead to transitions whose lifetimes are several hundred times the single-particle estimate. In light nuclei, some transitions are inhibited by an isobaric-spin effect. Theroetical values are obtained for comparison with some recently measured lifetimes in the region around . Both quadrupole deformation and the isobaric-spin effect can contribute to inhibitions in this region. The isobaric-spin effect is sufficient to account for the lifetimes in and . For nuclei further removed from , the effect of deformation is also necessary. In some simple examples we show that such a trend results from the nature of the particle-hole interaction.
- Received 7 April 1967
- Published in the issue dated September 1967
© 1967 The American Physical Society