Studies of Size Selected Metal and Semiconductor Clusters

Studies of the chemical reactions and photodissociation of size selected Al sup + sub n, Si sup + sub n, and Cu sup + sub n with n upto 30 will be described. The chemical reactions have been studied by injected ion drift tube techniques, which allows us to investigate the temperature dependence of the reaction rate constants. The photodissociation studies have been performed on a novel experiment where dissociation lifetimes can be directly measured. Simulations of the measured lifetimes (as a function of internal energy) by RRKM theory provides accurate values for the dissociation energies of the clusters as a function of size. The results will be compared with the predictions of ab initio theory and simple empirical models for the development of the bulk cohesive energy in these microscopic particles.