Negative heat capacities and first order phase transitions in nuclei and other mesoscopic systems

TL;DR

This paper explains anomalies in caloric curves of nuclei and mesoscopic systems by showing that evaporative shrinking causes negative heat capacities and backbending in caloric curves, indicating first-order phase transitions.

Contribution

It demonstrates that evaporation-induced reduction in system size explains negative heat capacities, providing a thermodynamic basis for observed anomalies in mesoscopic systems.

Findings

Backbending in caloric curves observed in nuclei.

Negative specific heats occur in the two-phase coexistence region.

Shrinking of the system's radius causes the anomalies, not additional surface energy.

Abstract

The origin of predicted and observed anomalies in caloric curves of nuclei and other mesoscopic systems is investigated. It is shown that a straightforward thermodynamical treatment of an evaporating liquid drop leads to a backbending in the caloric curve and to negative specific heats in the two phase coexistence region. The cause is found not in the generation of additional surface, but in the progressive reduction of the drop's radius, and surface, with evaporation.