Professor Dagdigian is supported by a grant from the Experimental Physical Chemistry Program to study the chemical reactions between fragments of molecules in crossed molecular beams by analysing the light emitted by the products upon laser excitation. The motivation for these studies is to answer the question: What is the effect of having many possible potential energy surfaces on which these reactions occur on the distribution of product molecules and on the energy states in which they are produced? In this project the dynamics of reactions involving molecular free radicals will be experimentally investigated through the determination of product internal state distributions using the laser fluorescence detection technique. Because of the unpaired electrons on both reagents, these reactions necessarily involve multiple potential energy surfaces. The influence of the different surfaces should be manifest in the branching between different product channels. The reactions of oxygen atoms with vibrationally excited reagents, which will be prepared by stimulated Raman excitation, will be probed through measurement of the hydroxyl product internal distribution.