Studies of the formation of non-metallic microclusters and color center type defects in alkali halide clusters

In this dissertation, we have used a laser vaporization cluster source (LVCS) to study the formation of non-metallic clusters, and have applied various laser spectroscopic techniques to study color center type defects in alkali halide clusters. We have demonstrated that laser vaporization of non metallic solids can produce atomic or molecular clusters and cluster ions by direct ejection of fragments from the sample surface. The spectra of cluster ions M(MX){dollar}sbsp{lcub}rm n{rcub}{lcub}+{rcub}{dollar} and X(MX){dollar}sbsp{lcub}rm n{rcub}{lcub}-{rcub}{dollar} formed by vaporizing mixed alkali halide powder samples include virtually no alloyed species, indicating that the observed clusters do not grow from molecular vapor but are instead laser sputtered from the solid in a non-thermal shattering process. In carbon, large clusters result from partial evaporation of ultrafine particles on the sample. We have carried out mass spectroscopy, photodissociation, threshold and above threshold photoelectron spectroscopy studies of alkali halide clusters with color center defects. We have found that the incorporation of a defect may substantially change the cluster's ground state geometry. Particularly, for a stoichiometric alkali halide cluster anion, which has one excess electron and is analogous to an F center, the excess electron can bind inside the cluster in one of several ways that range from being delocalized throughout the cluster or at its surface as a conduction electron, to occupying a crystalline lattice site as though it were a halogen ion.