Unified Model Studies of N = 84 and N = 80 Nuclei

Abstract

The unified model which couples two valence nucleons to collective quadrupole surface vibrations is applied to the N= 84.and N = 80 nuclei which have respectively two neutrons and two neutron holes outside the closed N = 82 core. Two different interactions between these valence nucleons are considered. The first is a simple pairing interaction, and the second used matrix elements determined in a bare G matrix calculation. The simple pairing force gives much better results. A two step diagonlization is employed to treat the core and -valence nucleons consistently. Up to four phonons are retained in the collective basis and the diagonalized (coupled) valence nucleon space is truncated at approximately the same energy. The experimental spectra and electromagnetic properties are well-reproduced for both types of nuclei, and in the N 84.nuclei the four phonon contribution was found to be non-negligible. In addition, a closed form, multiplicity resolved expression for matrix elements of (αthe collective surface coordinate) is presented, and a table of these values for N < 6 is given.