Photothermodissociation of selenium clusters

The dissociation of selenium cluster ions containing from 7 up to 30 atoms has been studied using unimolecular decay of photothermoexcited clusters. C lusters containing more than 14 atoms evaporate Se-6, Se-7, and Se-8 specie s, whereas smaller clusters with 7-10 atoms dissociate manly by Se-2 loss. When the size increases, Se-6 becomes the predominant channel showing a dis sociation which evolves toward the bulk behavior. The changes in the observ ed channels correlate to changes in the dissociation energies which are ded uced from the measured fractional dissociation rates and from the entropy c ontribution. Together with the previous study of tellurium clusters, this w ork provides comparative behavior of dissociation energies of group VI clus ters and their convergence toward bulk properties. (C) 2000 American Instit ute of Physics. [S0021-9606(00)00223-3].