Our research program seeks to understand the microscopic dynamics of chemical reactions in solution. Using femtosecond (10-15 s) duration laser pulses we can rapidly photoexcite chemical species in the condensed phase and then probe the ensuing dynamics on the timescale of elementary molecular motions. The experiments provide a detailed picture of many of the very fastest chemical reactions, often revealing surprising mode-specific effects. We are particularly interested in the reaction dynamics of optically generated radicals. Reactions involving both charged and uncharged radicals are under investigation to determine the influence of the local liquid environment on radical recombination reactions, cage escape and reactions with solvent molecules. Time-resolved spectroscopy frequently allows us to distinguish between intramolecular and intermolecular routes for energy disposal following photoexcitation. Work is also underway to prepare coherent states (wavepackets) by two-photon absorption for studying the unusual photochemistry of higher-lying electronic states in solution. One aspect of this work is aimed at understanding the condensed-phase photoionization of small biomolecules. Extensions of our dynamical studies in bulk solvents to chemical reactions near interfaces are planned.
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