Picosecond Processes in Chemical Systems: Vibrational Relaxation

A review is presented of our recent studies of vibrational energy relaxation of moderately sized molecules in a variety of media and of the effect of vibrational relaxation on processes such as molecular rearrangements.Data are presented on intramolecular dynamical processes involving p-difluorobenzene and an experiment is described which allows the study of spectral evolution on the picosecond timescale under collision-free conditions.The vibrational (T1) relaxation of the apparently simple system consisting of a diatomic CN− ion in aqueous solution was studied and found to be in the range of a few picoseconds and to be concentration dependent. These results, and the effects of counterions, are suggested to be the result of aggregation of the ions. A discussion of the Raman lineshapes is given in relation to the measured T1 times.