Evolution of nuclear collectivity: empirical phenomenology and model interpretation

The energies of low-spin yrast states, E (21+) and E (41+), and the transition probabilities, B (E2; 21+ → 0 1+), that are among the most revealing and the easiest to measure observables of collectivity, show global correlations that help our understanding of nuclear structure and nuclear phase transitions and provide new signatures to identify particular structures. These correlations combined with the behavior of two neutron separation energies show that the nuclear system presents a shape transition in its evolution from spherical vibrator to well deformed rotor. This behavior is supported by model calculations, as is the concept of phase/shape coexistence in the N ∼ 90 region. (author)