Probing the liquid-to-gas phase transition in a cluster via a caloric curve - art. no. 203401

High-energy collisions (60 keV/amu) of hydrogen cluster ions with a helium target have been completely analyzed on an event-by-event basis. By selecti ng specific decay reactions we can start after the energizing collision wit h a microcanonical cluster ion ensemble of fixed excitation energy and we d erive corresponding temperatures of the decaying cluster ions. The relation between the temperature and the excitation energy (caloric curve) exhibits the typical prerequisites of a first-order phase transition in a finite sy stem, in the present case signaling the transition from a bound cluster to the gas phase.