Laser Flash Photolysis Studies of Radical-Radical Reaction Kinetics: The HO↓(2) + BrO Reaction

摘要

Laser flash photolysis of CI↓(2)/CH↓(3)OH/O↓(2)/Br↓(2)/O↓(3)/N↓(2) mixtures at 308 nm has been coupled with simultaneous time-resolved detection of HO2 (by infrared tunable diode laser absorption spectroscopy) and BrO (by ultraviolet absorption spectroscopy) to investigate the kinetics of the important stratospheric reaction HO↓(2) + BrO → products at 296 ± 3 K in N↓(2) buffer gas at pressures of 12 and 25 Torr. All experiments were performed under near pseudo-first-order conditions with HO↓(2) in excess over BrO. The HO↓(2) ＋ BrO rate coefficient is found to be k↓(1) = (2.0±0.6) ×10↑(-11) cm↑(3) molecule↑(-1)s↑(-1), with the primary source of uncertainty being knowledge of the infrared line strength(s) required to convert measured HO↓(2) absorbances to absolute concentrations. The rate coefficient for the reaction HO↓(2) + HO↓(2) →H↓(2)O↓(2) + O(2) derived based on infrared absorption measurements of the HO↓(2) concentration is consistent with the currently accepted value. The results reported in this study are compared with other recent studies of HO↓(2) + BrO kinetics, and their implications for our understanding of stratospheric chemistry are discussed.