EVIDENCE FOR THE DIRECT EJECTION OF CLUSTERS FROM ALKALI-HALIDES DURING LASER VAPORIZATION

We have studied the formation of clusters of alkali halides during laser vaporization. Measurements of the abundances of cluster ions produced by several different source configurations indicate that clusters are ejected directly from the source sample and do not necessarily grow from an atomic or molecular vapor. Using samples consisting of mixed alkali halide powders, we have found that unalloyed clusters are easily produced in a source that prevents growth from occurring after the clusters leave the sample surface. Melting the sample or encouraging growth after vaporization lead to the production of alloyed cluster species. We also obtain information about the relative binding energies for substituted halogen ions bound to alkali halide clusters.