Probing the liquid-to-gas phase transition in a cluster via a caloric curve.
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 selecting specific decay reactions we can start after the energizing collision with a microcanonical cluster ion ensemble of fixed excitation energy and we derive 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 system, in the present case signaling the transition from a bound cluster to the gas phase.
Gobet
F
F
Institut de Physique Nucléaire de Lyon, IN2P3-CNRS et Université Claude Bernard Lyon 1, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France.
Farizon
B
B
Farizon
M
M
Gaillard
M J
MJ
Buchet
J P
JP
Carré
M
M
Märk
T D
TD