A laser photolysis time-resolved Fourier transform infrared emission study of OH(X 2Π, v) produced in the reaction of alkyl radicals with O(3P)

The emission spectra of vibrationally excited hydroxyl radical products formed in the reactions of alkyl radicals with O(P-3) atoms are detected using a laser photolysis/time-resolved Fourier transform infrared spectroscopy technique. For the reaction between oxygen atoms and ethyl, the radicals are produced simultaneously by the 193 nm photolysis of the precursors SO2 and diethyl ketone, respectively. The observed initial OH(upsilon) product vibrational state distribution for the C2H5 + O(P-3) reaction is 0.18 +/- 0.03, 0.23 +/- 0.04, 0.29 +/- 0.05, 0.23 +/- 0.07, and 0.07 +/- 0.04 for upsilon = 1 to 5, respectively. The population inversion is best explained by a direct abstraction mechanism for this radical-radical reaction. Vibrationally excited hydroxyl radicals are also observed in the O + ethyl, O + n-propyl, and O + i-propyl reactions when using alkyl iodides as precursors of the alkyl radicals, although quantitative detail is not obtained due to competing reaction processes. (C) 1998 American Institute of Physics.