Microscopic calculations of nuclear level densities with the Lanczos method

Abstract

A new method for computing the density of states in nuclei making use of an extrapolated form of the tri-diagonal matrix obtained from the Lanczos method is presented. It will be shown that the global, average properties of the entire Lanczos matrix can be predicted from just four Lanczos iterations. The extrapolated Lanczos matrix (ELM) approach provides for an accurate computation of the density of states described within the configuration space, which, in some cases, is sufficient to accurately calculate the density of states at, or near, the neutron separation energy. Comparisons between theory and experiment are shown for $^{57}$Fe, $^{74}$Ge, and $^{76}$Ge. In addition, we show results for the $J$-dependence of moments and the level density for these three nuclei.