SHELL-MODEL STUDIES OF THE Y-90,ZR-91,NB-92 AND MO-93 NUCLEI

A shell-model calculation of the N = 51, 39 ≦ Z ≦ 42 nuclei is presented. The 88Sr nucleus is assumed to be an inert closed core. The extra-core protons are restricted to the (2p 1 2, 1g 9 2) configurations, and the active neutron is allowed to occupy the 2d 5 2, 3s 1 2, 2d 3 2 and 1g 7 2 orbits. The proton-proton effective interaction is directly taken from the previous analysis on the energy levels for N = 50 isotones by Ball et al. The proton-neutron effective interaction is assumed to be of the form of the surface δ-interaction. The energy spectra are calculated from a least-squares fit to the experimental data, varying the T = 0 and T = 1 strengths of the surface δ-interaction. Spectroscopic factors, E2 transition rates and two-body matrix elements are also calculated and compared with the observed values and the previous theoretical results. © 1979.