Parity Dependent Shell Model Level Densities for Nuclear Astrophysics

Abstract

Recently, we developed a methodology [1-4] of calculating the spin and parity dependent shell model nuclear level density, which is a very useful ingredient in the Huaser-Feshbach theory for calculating reaction rates for nuclear astrophysics[5]. We developed new techniques based on nuclear statistical spectroscopy [6] to calculate the spin and parity projected moments of the nuclear shell model Hamiltonian, that can be further used to obtain an accurate description of the nuclear level density up to about 15 MeV excitation energy. These techniques were fully tested for the sd-shell nuclei and some light f p-shell nuclei, by comparing with the level density obtained from exact shell model diagonalization. Here we present for the first time comparisons with the exact shell model diagonalization for nuclei heavier than 56Ni, in a model space spanned by the f5/2, p3/2, p1/2 and g9/2 orbits. The ratio of nuclear level densities of opposite parities is also discussed. This analysis was possible due to a new and very efficient nuclear shell model code [7] that can provide a large number of states of given spin and parity.