ENERGY-RESOLVED STUDIES OF PHOTOCHEMISTRY ON SEMICONDUCTOR SURFACES

The investigation of the dynamics of optically driven chemical processes on surfaces is providing new insight into how the presence of a solid surface alters the mechanisms, energetics, and fragmentation patterns seen in isolated-molecule photochemistry. This paper reviews recent work on the photodissociation dynamics of molecular adsorbates on semiconductor surfaces, emphasizing energy-resolved measurements of the desorbed fragments. The results of this research show that the mechanisms and energetics for photofragmentation for molecules at the top of thick condensed layers are very close to those of the gas phase. At low coverages, however, electron-transfer reactions dominate and direct photon-assisted chemistry is quenched.