In this project in the Physical Chemistry Program of the Chemistry Division, Graham Fleming of the University of Chicago will examine chemical dynamics in condensed phases on a femtosecond time scale. Ultrafast spectroscopy and non-linear spectroscopic techniques will be used to probe the molecular dynamics in solution which are usually masked by the featureless nature of liquid-phase electronic spectra. Ultrashort pulses will be combined with pulse sequences to study the full range of time scales present in the experimental system and its solvent. Structures to be studied include biological systems with a photosynthetic reaction center. Various chemical phenomena such as electron transfer will be rationalized and predicted using spectral densities. The cage effect on the dissociation of iodine will be observed to determine the mechanism of solvent-induced curve crossing. This research will attempt to find examine several issues. One involves the effect of solvent molecules in liquid solutions on reactions in an attempt to determine, for example, under what conditions the solvents form cages around reactive species and keep them close enough for reaction to occur. Do these solvent molecules modify the reactive condition of these reagent molecules? How are proteins affected in the water solutions which are characteristic of living systems? These experiments will also examine some aspects of the mechanism of photosynthesis in order to gain a fuller understanding of this important life process.
