Statistical theory of deformation distributions in nuclear spectra

Abstract

The dependence of the nuclear level density on intrinsic deformation is an important input to dynamical nuclear processes such as fission. Auxiliary-field Monte Carlo (AFMC) method is a powerful method for computing nuclear level densities. However, the statistical distribution of intrinsic shapes is not readily accessible due to the formulation of AFMC in a spherical configuration-interaction shell-model approach. Instead, theory of deformation up to now has largely relied on a mean-field approximation which breaks rotational symmetry. We show here how the distributions of the intrinsic quadrupole deformation parameters can be calculated within the AFMC method, and present results for a chain of even-mass samarium nuclei (${}^{148}$Sm, ${}^{150}$Sm, ${}^{152}$Sm, ${}^{154}$Sm) which includes spherical, transitional, and strongly deformed isotopes. The method relies on a Landau-like expansion of the Helmholtz free energy in invariant polynomials of the quadrupole tensor. We find that an expansion to fourth order provides an excellent description of the AFMC results.

13 pages, 11 figures

References in corpus (8)

• Symmetry-guided large-scale shell-model theory
• Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities
• Heavy deformed nuclei in the shell model Monte Carlo method
• Crossover from vibrational to rotational collectivity in heavy nuclei in the shell-model Monte Carlo approach
• Shell model based deformation analysis of light Cadmium isotopes
• Nuclear deformation at finite temperature
• Nuclear deformation in the laboratory frame
• Auxiliary-field quantum Monte Carlo methods in nuclei

Cited by in corpus (7)

• Physics of nuclei: Key role of an emergent symmetry
• Constraining the quadrupole deformation of atomic nuclei with relativistic nuclear collisions
• Efficacy of the symmetry-adapted basis for ab initio nucleon-nucleus interactions for light- and intermediate-mass nuclei
• Shape coexistence in Sr isotopes
• State densities of heavy nuclei in the static-path plus random-phase approximation
• Nuclear level densities: from empirical models to microscopic methods
• The impact of nuclear deformation on relativistic heavy-ion collisions: assessing consistency in nuclear physics across energy scales