State-resolved product detection in the overtone vibration initiated unimolecular decomposition of HOOH(6νOH)

Abstract

Excitation of reactant overtone vibrations in combination with laser induced fluorescence detection of unimolecular decomposition products permits measurements of reactant vibrational overtone excitation spectra and product state distributions for selectively excited hydrogen peroxide and its partially deuterated analog. The hydrogen peroxide excitation spectrum in the region of the fifth OH overtone vibration (6νOH) shows a pure local mode feature along with several others that are apparently combinations of a local mode vibration with a normal mode vibration. The product state distributions show substantial energy release into rotation with some molecules having rotational excitation approaching the limit of the total energy available. A statistical calculation incorporating conservation of total angular momentum and energy describes the observed distributions quite well for excitation of the pure local mode vibration. The products from excitation of a combination transition are in a distribution of states that differs qualitatively from a statistical outcome, possibly indicating selective energy coupling on the time scale of the unimolecular reaction.