QUASI-PARTICLE DESCRIPTION OF 2+ AND 3- STATES OF DOUBLY EVEN SPHERICAL NUCLEI

The description of the first 2+ and 3- levels of spherical nuclei 90 ≦ A ≦ 150 and 186 ≦ A ≦ 206 is performed in the framework of the BCS theory. The residual interaction is taken as the superposition of the pairing force and of the multipole force. The short-range proton-neutron correlations are neglected. In addition to the valence nucleons, the core particles are taken into account; it allows the computation of the transition probabilities without any effective charge. Theoretical predictions concerning the E2+ and E3- energies, the B(E2) and B(E3) reduced transition probabilities and the gyromagnetic factors g2+ are in good agreement with experiment. © 1968.