Reactions of HO2 with NO and NO2 studied by mid-infrared laser magnetic resonance

Abstract

The technique of mid-infrared laser magnetic resonance spectroscopy combined with a discharge-flow system has been used to study reactions of the HO₂ radical at total pressures up to 13 Torr, corresponding to conditions in the middle stratosphere.

The validity of the technique was confirmed by the determination of a rate coefficient of (8.5 ± 1.3)× 10^–12 cm³ molec^–1 s^–1 at 297 K for the reaction HO₂+ NO → OH + NO₂ in excellent agreement with previous studies. The reaction HO₂+ NO₂+ M → HO₂NO₂+ M was also studied. For M = He, the rate coefficient is (6.0 ± 1.5)× 10^–32 cm⁶ molec^–2 s^–1 at 297 K, while the data for M = Ar were fitted by the expression 1.24 × 10^–31(T/300)^{–2.37±0.16} cm⁶ molec^–2 s^–1 between 275 and 326 K.