Kinetics of the gas-phase reactions of OH with NO2 and with NO

Abstract

The kinetics of the reaction, OH + NO₂+ M → HNO₃+ M (1), have been reinvestigated in order to provide data, using the same apparatus, for a series of third bodies, M. A discharge-flow–resonance-fluorescence technique was used to obtain third-order rate constants in the pressure range 1–5 Torr for M = He, Ar, N₂, O₂ and CO₂. At T= 295 ± 3 K, the values of k₁/10^–31 cm⁶ molecule^–2 s^–1 were He, 16 ± 1; Ar, 16 ± 3; N₂, 27 ± 2; O₂, 26 ± 7; CO₂, 45 ± 10 (95% confidence limit errors; systematic errors could contribute an additional 20% range). Similar investigations of the reaction, OH + NO + M → HONO + M (2), for M = He, Ar and N₂ gave values of k₂/10^–31 cm⁶ molecule^–2 s^–1 of He, 6.0 ± 0.3; Ar, 7.4 ± 2.4; N₂, 11 ± 1. The implications of the results for the atmospheric chemistry of Earth, Mars and Venus are discussed.