This research, to be conducted in the Department of Chemistry at the University of California, San Diego, will utilize time-resolved laser spectroscopy to probe for evidence of solvent cage effects on Lewis acid base reactions. The acid-base pair will be generated by photolytic dissociation of a ligand from a six-coordinate, iron-porphyrin complex. Changes in temperature and/or pressure will be used to extend the temporal range of the spectroscopic experiments, which will be helpful in determining what portion of the reaction occurs in the solvent cage and what occurs after diffusion of the reagents out of the solvent cage. %%% Professor Douglas Magde of the Department of Chemistry at the University of California, San Diego will conduct experiments on pairs of reactant molecules generated in close proximity in solution. Subsequent reactions of these molecules will be monitored using rapid spectroscopic methods to determine whether the surrounding solvent molecules provide a cage effect that serves to hold the reactants together, or whether the molecules are totally free to move apart and react later in a subsequent encounter. These studies are designed to provide fundamental information important for all reactions that occur in solution. The reactants chosen for study are related to biological oxygen carriers so that the results will have special applicability to biological functions.