A fully microscopic model of total level density in spherical nuclei

Abstract

A fully microscopic model for the description of nuclear level density (NLD) in spherical nuclei is proposed. The model is derived by combining the partition function of the exact pairing solution plus the independent-particle model at finite temperature (EP+IPM) with that obtained by using the collective vibrational states calculated from the self-consistent Hartree-Fock mean field with MSk3 interaction plus the exact pairing and random-phases approximation (SC-HFEPRPA). Two important factors are taken into account in a fully microscopic way, namely the spin cut-off and vibrational enhancement factors are, respectively, calculated using the statistical thermodynamics and partition function of the SC-HFEPRPA without any fitting parameters. The numerical test for two spherical ${}^{60}$Ni and ${}^{90}$Zr nuclei shows that the collective vibrational enhancement is mostly dominated by the quadrupole and octupole excitations. This is the first microscopic model confirming such an effect, which was phenomenologically predicted long time ago and widely employed in several NLD models. In addition, the influence of collective vibrational enhancement on nuclear thermodynamic quantities such as excitation energy, specific heat capacity and entropy is also studied by using the proposed model.

arXiv comment7 pages, 3 figures, accepted in Phys. Lett. B

References in corpus (13)

• Astrophysical Reaction Rates From Statistical Model Calculations
• Nuclear Level Density and the Determination of Thermonuclear Rates for Astrophysics
• Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities
• Particle-Number Reprojection in the Shell Model Monte Carlo Method: Application to Nuclear Level Densities
• Nuclear level statistics: extending the shell model theory to higher temperatures
• Crossover from vibrational to rotational collectivity in heavy nuclei in the shell-model Monte Carlo approach
• Test of nuclear level density inputs for Hauser-Feshbach model calculations
• Level densities of nickel isotopes: microscopic theory versus experiment
• Giant dipole resonance in ${}^{201}$Tl at low temperature
• Thermal properties of a rotating nucleus in a fluctuating mean field approach
• On the angular momentum dependence of nuclear level densities
• Level density and level density parameter in medium heavy nuclei including thermal and quantal fluctuation effects
• SPA+RPA approach to canonical and grandcanonical treatments of nuclear level densities