The Theoretical and Computational Chemistry Program of the Chemistry Division is supporting research by Lionel Raff at Oklahoma State University on the theoretical investigation of chemical processes under matrix isolation conditions. The studies include reaction dynamics, energy transfer, mobility, and diffusion of fluorine, oxygen, hydrogen, deuterium, and tritium atoms in matrices of argon, krypton, and xenon. Further, addition reactions of fluorine and chlorine to ethylene and of HBr to acetylene and subsequent elimination reactions are being investigated. %%% Many chemical reactions and spectroscopic properties can be studied most effectively by freezing the species of interest in a matrix consisting of an inert gas. This research involves a theoretical investigation of the dynamics of such reactions as well as molecular mobility and energy transfer under such conditions.