Topics in current nuclear structure: Effects of the p-n interaction on nuclear collectivity and signatures of gamma softness and triaxiality

This talk discusses two topics of current and long-standing interest. The first concerns the pervasive effects of the residual valence proton-neutron interaction on nuclear collectivity and initially focuses on some very simple evidence for its role in nuclear collectivity and then turns to a discussion of recent extractions of empirical p-n interaction matrix elements for even-even nuclei and attempts to understand them via simple Shell Model and Nilsson Model calculations. The second topic centers on empirical signatures that distinguish γ softness from γ rigidity, based on the low-energy low-spin nuclear regime. Results for all even-even nuclei will be compared to model predictions including an approach that simulates changing γ softness for γrms∼30 degree. It is shown that all nuclei above A = 60 that display axial asymmetry exhibit a strong preference for γ softness rather than triaxiality