Paul Houston of Cornell University is supported by the Experimental Physical Chemistry Program to continue his studies on photodissociation dynamics. Specifically, he will focus his efforts in two areas: a) photodissociation dynamics of small free radicals, where comparison with theory is very fruitful, and b) photodissociation dynamics of state-selected molecules, where it is possible to observe the influence of the initial excitation on the product distribution. The studies on radicals will not only provide an experimental benchmark for theoretical chemists, but will also have a large impact in the areas of atmospheric and combustion chemistry. The state-selected precursor/state-resolved product experiments will contribute tremendously to further our understanding of collision dynamics.