Spectroscopy and dynamics of intermediates involved in the oxidation of saturated and unsaturated hydrocarbons.

摘要

Oxidation of volatile organic compounds (VOC) is an important process in atmospheric and combustion chemistry. VOC consist of different saturated and unsaturated hydrocarbons and other organic molecules. Different intermediates like alkyl peroxy and alkoxy radicals are involved in the oxidation of VOC. Spectroscopy of these intermediates can provide information on their structures and their fate in the chemical reactions they are involved in.;Different experimental techniques like cavity ring down spectroscopy (CRDS) and laser induced fuorescence (LIF) spectroscopy were used to obtain spectra for the electronic transitions of different intermediates involved in the oxidation of ethene and propane. Vibronic analyses were performed for the experimental spectra with the aid of quantum chemistry calculations. Accurate transition origin positions, excited state vibrational frequencies and rotational constants were determined for the first time for different intermediates such as beta-hydroxyethyl peroxy, β-fluoroethoxy and isopropoxy.;Fragmentation of different halogen (F, Cl and Br) and hydroxy substituted ethyl nitrite upon 351nm photo-dissociation was also studied as substituted ethyl nitrite are known precursor molecules for the production of substituted ethoxy radicals. Formaldehyde and vinoxy fragments were identified via their rotationally resolved spectra in these experiments. Observation of these fragments were explained by analysis of different reaction pathways calculated via quantum chemistry calculations.