Drs. John B. Hopkins and Carl F. Knopf are supported by a grant from the Theoretical and Computational Chemistry Program to perform ultrafast transient Raman spectroscopic investigations of reactions occuring in supercritical fluids. The goal of this research is to understand the role which solvent plays in condensed phase chemical reactions. The main thrust of the research is to investigate solvent effects on chemical dynamics near the critical point of atomic and small polyatomic solvents. Drs. Hopkins and Knopf will attempt to characterize the local solvent density in clusters surrounding infinitely dilute solute molecules near the critical point by directly measuring the density dependence of vibrational energy relaxation in diatomic solute molecules. They will also investigate the effect of local solvent density on chemical dynamics using ultrafast laser studies of photodissociation and geminate recombination reactions. Direct real time investigations will focus on understanding the role of 1) solvent clusters and dynamic density fluctuations, 2) van der Waals complexes, and 3) energy transfer in determining reactivity at different fluid densities.
