The Statistical Multifragmentation Model with Skyrme Effective Interactions

TL;DR

This paper enhances the Statistical Multifragmentation Model by integrating Skyrme effective interactions via the finite temperature Thomas-Fermi approximation, revealing phase transition features and sensitivities in nuclear fragmentation observables.

Contribution

It introduces a novel way to incorporate Skyrme interactions into the model, allowing for more accurate predictions of nuclear phase transitions and fragment distributions at finite temperatures.

Findings

Observation of a plateau in the caloric curve at 8-10 MeV/nucleon

Detection of a negative heat capacity region at the gas transition

Sensitivity of isotopic distributions to free energy calculations

Abstract

The Statistical Multifragmentation Model is modified to incorporate the Helmholtz free energies calculated in the finite temperature Thomas-Fermi approximation using Skyrme effective interactions. In this formulation, the density of the fragments at the freeze-out configuration corresponds to the equilibrium value obtained in the Thomas-Fermi approximation at the given temperature. The behavior of the nuclear caloric curve at constant volume is investigated in the micro-canonical ensemble and a plateau is observed for excitation energies between 8 and 10 MeV per nucleon. A kink in the caloric curve is found at the onset of this gas transition, indicating the existence of a small excitation energy region with negative heat capacity. In contrast to previous statistical calculations, this situation takes place even in this case in which the system is constrained to fixed volume. The observed phase transition takes place at approximately constant entropy. The charge distribution and other observables also turn out to be sensitive to the treatment employed in the calculation of the free energies and the fragments' volumes at finite temperature, specially at high excitation energies. The isotopic distribution is also affected by this treatment, which suggests that this prescription may help to obtain information on the nuclear equation of state.