State-to-state studies of intramolecular dynamics

摘要

Infrared-optical double resonance incorporating vibrational overtone excitation of a light atom stretch mode prepares reactant molecules in single quasibound rovibrational states at energies above their decomposition threshold on the ground potential surface. When combined with laser induced fluorescence detection of the dissociation fragments, this approach permits fully quantum state resolved studies of unimolecular dissociation reactions. This report describes the application of this technique to study the unimolecular dissociation of hydrogen peroxide from a variety of vibrational and rotational states. We emphasize here the spectroscopy associated with the reactant excitation process and demonstrate how highly resolved excitation spectra provide detailed information about the dynamics of the ensuing dissociation. We then describe a new spectroscopic technique for detecting vibrational overtone excitation in low pressure environments based upon selective CO$-2$/ laser infrared multiphoton dissociation of highly vibrationally excited molecules. We show preliminary results applying this approach to CH$-3$/OH.