Excited electronic states and optical spectra of ZnS and CdS crystallites in the ~ 15angstroms to 50angstroms size range: Evolution from molecular to bulk semiconducting properties.

The valence electrons in sp(3) hybridized semiconductors are strongly delocalized. This delocalization implies that the electronic and optical properties of the bulk crystalline solid develop gradually as a small cluster of the material grows in size. Small clusters have properties that are partially molecular in nature. This memorandum is part of an experimental program to make and characterize such clusters (=50angstroms diameter). Our goal is to understand the chemical physics of the evolution of bulk properties.