MICROSCOPIC FRICTION AND SOLVATION IN BARRIER CROSSING - ISOMERIZATION OF STILBENE IN SIZE-SELECTED HEXANE CLUSTERS

In order to understand the roles of bulk friction and solvation in bar rier crossing reactions, here we report our first study of the isomeri zation rates for a beam of t-stilbene-hexane(n) clusters, n=1-5, at ex cess energies covering the range E(ex)= 0-4000 cm(-1). We observe that rates measured at excess energies well above the t-stilbene isomeriza tion barrier decrease monotonically with increasing number of solvent molecules. The influence of microscopic solvation on the rates is syst ematically studied and related to changes in barrier height and intern al friction, both key to the understanding of behavior in the bulk.