SHELL-MODEL STUDY OF THE HIGH-SPIN STATES IN THE N=50 ISOTONES MO-92,TC-93, RU-94, AND RH-95

The low lying levels in N=50 isotones have been well described within the shell model framework. These calculations were performed assuming an inert neutron core and the valence protons occupying either the (p( 1/2),g(9/2)) or (f(5/2),p(3/2),p(1/2),g(9/2)) orbits. With the advent of multidetector arrays the level schemes of these nuclei have been ex tended to high spin regimes (J=20-25HBAR). The inclusion of neutron co re excitation (neutron particle-hole excitation across the N=50 shell gap) was essential to adequately describe these observed higher angula r momentum states. Calculations involving neutron particle-hole excita tion across the N=50 shell gap, coupled to the lower valence proton co nfigurations, were not feasible due to computational limitations. This paper describes a truncation scheme devised to perform large basis sh ell model calculations. The level sequences observed in the N=50 isoto nes Mo-92, (TC)-T-93, Ru-94, and Rh-95 are interpreted on the basis of the shell model calculations in the configuration space f(5/2), p(3/2 ), p(1/2) , g(9/2) for the protons and p(1/2), g(9/2), g(7/12), d(5/2) , d(3/2), S-1/2 for the neutrons. The excitation of a g(9/2) neutron a cross the N=50 shell, into the next major oscillator shell describes t he observed higher angular momentum states in these nuclei.