Experimental Evidence for the Entropy Effect in Coulombic Cluster Fission.

Abstract

Coulombic fission of warmed triply charged potassium ion clusters ${\mathrm{K}}_{n}^{3+}$, with $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}54$--105, is studied by unimolecular dissociation mass spectroscopy. Binary fission is shown to occur predominantly with an asymmetrical character which attenuates as the size of the cluster increases. Such a result cannot be interpreted by energetic considerations unless the entropy contribution of discrete atoms is taken into account.