Formation of O2(a1Δg) and vibrationally excited OH in the reaction between O atoms and HOx species

Abstract

The first excited state of molecular oxygen [O₂(a¹Δ_g)] has been observed in the reaction between H atoms and O₃. It is shown that the most likely mechanism for the generation of the excited species is a branch of the reaction O + OH(v 1)→ O₂+ H (1a) that leads to O₂(a¹Δ_g) O + OH(v 1)→ O₂(a¹Δ_g)+ H. (1b) It is estimated that reaction (1b) contributes ca. 2.5% to the overall reaction (1a). Chemiluminescence from OH(v⩽6) has been observed in the reaction between O atoms and HO₂. Implications for atmospheric airglow chemistry are discussed.