Abstract
By selecting specific decay reactions in high-energy collisions () of hydrogen cluster ions with a helium target (utilizing event-by-event data of a recently developed multicoincidence experiment) and by deriving corresponding temperatures for these microcanonical cluster ensembles (analyzing respective fragment distributions), we are able to construct caloric curves for cluster ions (). All individual curves and the mean of these curves show a backbending in the plateau region, thus constituting direct evidence for a negative microcanonical heat capacity in the liquid-to-gas transition of these finite systems.
- Received 5 May 2002
DOI:https://doi.org/10.1103/PhysRevLett.89.183403
©2002 American Physical Society