Signatures for shape coexistence and shape/phase transitions in even–even nuclei

Abstract

Systematics of B(E2) transition rates connecting the first excited state to the first excited state of the ground state band in even–even nuclei indicates that shape coexistence of the ground state band and the first excited K = 0 band should be expected in nuclei lying within the stripes of nucleon numbers 7–8, 17–20, 34–40, 59–70, 96–112 predicted by the dual shell mechanism of the proxy-SU(3) model, avoiding their junctions, within which high deformation is expected. Systematics of the excitation energies of the states in even–even nuclei show that shape coexistence due to proton-induced neutron particle-hole excitations is related to a first-order shape/phase transition from spherical to deformed shapes, while shape coexistence due to neutron-induced proton particle-hole excitations is observed along major proton shell closures.