Negative heat capacity for hot nuclei: confirmation with formulation from the microcanonical ensemble

TL;DR

This paper confirms the existence of negative heat capacity in hot nuclei, indicating a first order phase transition, by analyzing experimental collision data with a microcanonical ensemble approach.

Contribution

It introduces a microcanonical formulation to analyze freeze-out properties of hot nuclei, confirming negative heat capacity with a new method.

Findings

Negative heat capacity observed in hot nuclei.

Confirmation of phase transition in finite nuclear systems.

Results consistent with previous studies.

Abstract

By using freeze-out properties of multifragmenting hot nuclei produced in quasifusion central $^{129}$Xe+$^{nat}$Sn collisions at different beam energies (32, 39, 45 and 50 AMeV) which were estimated by means of a simulation based on experimental data collected by the $4\pi$ INDRA multidetector, heat capacity in the thermal excitation energy range 4 - 12.5 AMeV was calculated from total kinetic energies and multiplicities at freeze-out. The microcanonical formulation was employed. Negative heat capacity which indicates a first order phase transition for finite systems is observed and confirms previous results using a different method.