Effective Interactions for Finite Nuclei

Large-scale shell-model calculations employing realistic effective interactions obtained from many-body theory have been rather successful in describing nuclear structure data both near and somewhat away from closed shells. In recent years such model calculations have been put to crucial test particularly in the Sn region, where experimental advances have provided us with a wealth of new data for nuclei with unusual proton and neutron numbers. In fact, level spectra are now available for essentially all the Sn isotopes from nucleon number A = 100 to A = 132, obtained by filling valence neutrons into the N = 4 major shell. This range of nuclei thus provides a testing ground for shell-model calculations in which one may study the transition from single-particle degrees of freedom to more collective ones away from closed shells, as well as the origin of possible underlying symmetries such as generalized seniority. Similarly, the N = 82 isotones beyond 132Sn provide us with the analogous valence proton spectra.