This research, part of the Experimental Physical Chemistry Program, is designed to study photochemistry of several prototypical systems at low temperatures. The research will elucidate the mechanisms of photolysis, identify intermediate species and elucidate their energy levels. Three systems are to be studied including the photolysis of dimethylacetylene, photoreactions of 1,4-diene systems and pseudo Jahn Teller interactions in phthalazine-alcohol complexes.