Rate of the OH + C₆H₆ + He reaction in the fall-off range by discharge flow and OH resonance fluorescence

Abstract

The rate constant k 1 of the reaction[Formula: see text]has been investigated by discharge flow resonance fluorescence of OH in the fall-off pressure range. From systematic measurements at five pressures between 0.5 and 9.5 torr, the Troe parameters k 0 and k ∞ (with F c = 0.6) have been derived at two temperatures: room temperature and 353 K. For room temperature, (297 ± 3) K, these parameters are k 0 = (1.7 ± 0.5) × 10 −29 cm 6 molecule −2 s −1 , k ∞ , = (10 ± 2) × 10 −13 cm 3 molecule −1 s −1 . Our experimental results are consistent with addition as the dominant path, in agreement with flash photolysis investigations and with the existence of a fast reaction with NO 2 of the (OH—benzene) radical adduct. A numerical simulation shows that this latter reaction should have a rate constant of (4 ± 2) × 10 −11 cm 3 molecule −1 s −1 at 353 K. Key words: gas phase kinetics, discharge flow, resonance fluorescence, reaction of OH with benzene, tropospheric chemistry.