Toward a Molecular Understanding of Quantum Chemical Dynamics in Solution

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Paul Barbara of the University of Texas is supported by a grant from the Theoretical and Computational Chemistry Program to continue his theoretical and experimental research directed at understanding quantum chemical dynamics in solution. Using femtosecond pump-probe optical spectroscopy as an experimental tool Barbara will study: 1) electronically nonadiabatic transitions in symmetric and asymmetric metal-metal intervalence compounds; 2) electronically nonadiabatic transitions in the one and two photon ionization of aqueous iodide solution and the two photon ionization of water; 3) vibrationally nonadiabatic transitions in the photodissociation, recombination, and the vibrational relaxation of small strongly solvated radicals with high frequency vibrations; and 4) the putative long-range coherent electron transfer between metallointercalators in DNA. Theoretical studies are also proposed of current quantum theoretical models for electron transfer and vibrational relaxation.Since many commercially important chemical reactions take place in polar solvents such as water, it is important to understand the influence which such solvents have on the reaction dynamics. A number of effects, such as solvent cage effects, vibrational relaxation and quantum mechanical tunneling, which are not present in the gas phase completely dominate condensed phase chemical reactions. It is important to develop reliable theories for model chemical systems which can then be applied to improving the efficiency of commercially important chemical reactions. The work which is being performed by Barbara provides an important experimental basis for the development of such theories.