📝 SummarXiv

Abstract

The study of heavy open-shell nuclei requires model spaces that are too large for the direct diagonalization approaches of conventional shell-model calculations. The shell-model Monte Carlo (SMMC) method enables calculations of the thermal properties of heavy nuclei in very large model spaces. Here, we extend the SMMC method to the actinides. Fifteen even-even and odd-mass actinides $^{232}$Th, $^{\textrm{234-239}}$U, $^{\textrm{240-243}}$Pu, $^{\textrm{246-248}}$Cm, and $^{250}$Cf are studied using a single-particle model space that is larger than one major shell each for protons and neutrons, with a total dimension of the many-particle space as large as $10^{32}$. We use spin projection methods to calculate nuclear level densities and average $s$-wave neutron resonance spacings, both of which are found to be in good agreement with recent experiments.