Product energy partitioning in the decompositiosn of state-selectively excited HOOH and HOOD

Abstract

Direct excitation of overtone vibrations is a highly selective energy-deposition technique which permits detailed studies of unimolecular reaction dynamics when combined with laser-induced fluorescence for state-resolved product detection. Applying this method to hydrogen peroxide and its partially deuterated analogue (HOOD) provides vibrational overtone excitation spectra of the molecules in the region of the v= 6 level of the OH stretching vibration and determines the OH or OD product rotational energy distributions. Partially deuterating HOOH produces a dramatic change in the shape of the pure stretching transition while other features, which apparently involve the deuterated portion of the molecule, move to lower frequencies. The decomposition products are formed in rotational states up to the limit of the available energy but have a markedly non-thermal distribution, with the populations decreasing sharply at high rotational levels. Detecting the OD fragment following excitation of the OH stretching transition in the parent molecule reveals an energy disposal pattern which is similar to that in the undeuterated case.