In this project of the Experimental Physical Chemistry Program in the Chemistry Division with support for instrumentation from the Office of Multidisciplinary Activities, Prof. L. Ziegler of Boston University will perform time-domain and spontaneous emission frequency-domain studies on ultrafast dynamics of solutions and neat liquids. The spontaneous resonance emission of short-lived photodissociative molecules in high-pressure gases (approaching liquid densities), liquids, and supercritical phases will be analyzed as a probe of time scales of solvation, optical dephasing and bath-induced nonadiabatic effects. Classical Molecular Dynamics simulation and instantaneous normal mode techniques will be used to analyze the experimental observations. Two extensions of femtosecond polarization spectroscopy, dispersed optical heterodyne detected (OHD) birefringence and dichroism of transparent liquids, will be developed. The role of two-photon absorption resonances in femtosecond pump-probe spectroscopy will be explored. Chemical reactions usually require the elevation of molecules to excited states of energy. Since the chemistry of molecules under conditions of high pressure, in solution, or embedded in a solid matrix or in a cluster is affected by their environment, it is important to know and understand these changes in order improve the technology based on chemical reactions. The research undertaken in this project will provide a data base and theoretical model for the reaction kinetics and dynamics of well characterized molecules which are embedded in a condensed phase medium. It also helps in the understanding of the outcome of many types of light-initiated chemical events.
