The role of quantum intramolecular dynamics in unimolecular reactions

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Abstract
The dynamics of unimolecular reactions can be modelled by classical mechanics for the motion of nuclei on Born-Oppenheimer or other effective potential surfaces, by the corresponding quantum mechanical equations of motion and, perhaps, by quantum statistical treatments. In this paper I provide a synopsis of fundamental, qualitatively important effects arising from the quantum nature of intramolecular dynamics, as opposed to classical mechanics, and illustrate these with theoretical predictions and experimental examples from the work of my group in Zurich. These include quantum nonlinearity in infrared (IR) multiphoton excitation and reaction, non-classical wavepacket spreading in the Fermi resonance coupled modes in CHX$_{3}$ molecules, effects of zero point energy and angular momentum in unimolecular reactions, nuclear spin symmetry conservation and interconversion and the hypothetical effects arising from the violation of parity and time reversal symmetry in unimolecular reactions. Specific applications to experiments include IR laser chemistry of CF$_{3}$I and CF$_{3}$Br, IR spectroscopy and dynamics of CHF$_{3}$ and predissociation spectra and dynamics of H$_{3}^{+}$.