State-to-state unimolecular reaction dynamics of highly vibrationally excited molecules

This article presents recent work investigating the unimolecular dissociati on rates of quantum state-selected molecules. Such studies provide the most stringent test for quantitative models of unimolecular reactions and their assumptions. After briefly reviewing the various experimental and theoreti cal techniques for state-resolved unimolecular dissociation rates, we prese nt results obtained in our laboratory using the method of double resonance overtone photofragment spectroscopy. We focus on the unimolecular dissociat ion of HOCl as a textbook case in which the dissociation rate is limited by slow intramolecular vibrational energy redistribution and give a simple mo del to treat this particular class of systems.