Cavity ringdown spectroscopy of intermediates in the reactions of aromatics + OH

Arom. compds., such as toluene and benzene, are important anthropogenically emitted volatile org. compds. in urban areas, and lead to the prodn. of secondary org. aerosols. However, there are many questions that remain about the mechanism of their atm. oxidn. and very few direct observations of the radial intermediates have been made. Therefore, we have used mid-IR pulsed-laser photolysis cavity ringdown spectroscopy to directly detect the hydroxy-cyclohexadienyl radicals formed from the addn. of OH to toluene and benzene in lab. expts. Vibrational spectra and kinetic models of the reaction chem. will be presented.