Microscopic nuclear level densities from Fe to Ge by the shell model Monte Carlo method

We calculate microscopically total and parity-projected level densities for β-stable even-even nuclei between Fe and Ge, using the shell model Monte Carlo methods in the complete (pf+0g9/2)-shell. A single-particle level density parameter a and backshift parameter Δ are extracted by fitting the calculated densities to a backshifted Bethe formula, and their systematics are studied across the region. Shell effects are observed in Δ for nuclei with Z=28 or N=28 and in the behavior of A/a as a function of the number of neutrons. We find a significant parity dependence of the level densities for nuclei with A≲60, which diminishes as A increases.