Alteration of photochemical events occurs when a molecule moves from the gas phase to an adsorbed phase. Sodium chloride, which is used as the substrate for adsorption, provides a vast array of relaxation channels for an excited molecule. These channels are available in the gas phase only at high pressure. At very low temperatures ( below 20 K) reactive species may be trapped on the surface for extended periods of time, allowing characterization by optical or magnetic spectroscopy. The research represents an inquiry into the use of ionic substrates as mediators in photochemical syntheses. Molecules physically adsorbed onto the surfaces of sublimated alkali halide films will be irradiated with the output of a tunable dye laser or with a He-Ne laser. Previous work has shown that decomposition is taking place with less than 20% efficiency based on the number of incident photons, the absorbance of the sample, and the detectability of products.