Study of Benzylperoxy Radical Using Laser Photolysis: Ultraviolet Spectrum, Self-Reaction, and Reaction with HO2 Kinetics

The ultraviolet absorption spectrum of benzylperoxy radical and the kinetics of the reactions 2C 6 H 5 CH 2 O 2 → products (I) and C 6 H 5 CH 2 O 2 + HO 2 → products (II) are studied. Experiments are carried out using the laser photolysis technique with time-resolved UV-visible absorption spectroscopy over the temperature range 298-353 K and the pressure range 50-200 Torr. The UV spectrum is determined relative to the known cross section of the ethylperoxy radical C 2 H 5 O 2 at 250 nm. Using factor analysis, the spectrum obtained is refined and the concentrations of the main absorbing species are extracted. The kinetic parameters are determined by analyzing and simulating the temporal profiles of the species concentrations and the experimental optical densities in the spectral region 220-280 nm. These are obtained using the recent UV spectra of the absorbing species existing in our mechanism. The Arrhenius expressions for reactions I and II are (cm 3 ·molecule -1 ·s -1 ) k I = 2.50 × 10 -14 e 1562/T and k II = 5.70 × 10 -14 e 1649/T . Our results are discussed and compared to literature data.