Multiple Laser Probes of Intramolecular Dynamics at Chemically Significant Energies

Abstract

Optical-infrared and infrared-optical double resonance schemes incorporating vibrational overtone excitation provide a new view of intramolecular vibrational energy redistribution (IVR) in dissociating molecules. In the first approach, an infrared predissociation spectrum of a molecule is recorded subsequent to light atom stretch overtone excitation. Such spectra directly reveal the extent of vibrational state mixing and the nature of the dark states involved in IVR at the excited level. The second approach employs infrared-optical double resonance to generate fully rotationally resolved vibrational overtone spectra of small molecules at energies above their unimolecular dissociation threshold. The spectral splittings and linewidths of single rotational transitions to dissociative states provide information about the rotational motion of a vibrationally excited molecule as it moves toward dissociation. These studies also reveal a marked vibrational mode dependence to the coupling matrix elements between the zeroth-order bright state and nearly isoenergetic dark states. This paper describes applications of these double resonance techniques to HOOH, HONO2and (CH3)3COOH.KeywordsVibrational StateOptical Parametric OscillatorDouble ResonanceBright StateDissociation ThresholdThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.