Abstract
Classical S matrix theory is used to describe photodissociation with the aid of the hyperbolic umbilic uniform approximation. A two degree of freedom model for CH3I, due to Shapiro and Bersohn, is studied and the uniform semiclassical results are found to be in good accord with exact quantum calculations. The semiclassical picture is also found to be an aid in understanding the more qualitative features of photodissociation. This leads to a modification of the original Shapiro and Bersohn model to bring the theoretical results into better agreement with experiment.