Kinetics of Active Oxygen Species with Implications for Atmospheric Ozone Chemistry

Abstract

Photochemical processes involving singlet oxygen (O2(a1Δ)), oxygen atoms, and ozone are critical in determining atmospheric ozone concentrations. Here we report on kinetic measurements and modeling that examine the importance of the reactions of vibrationally excited ozone. Oxygen atoms and O2(a1Δ) were produced by UV laser photolysis of ozone. Time-resolved absorption spectroscopy was used for O3 concentration measurements. It was found that vibrationally excited ozone formed by O + O2 + M O3(ν) + M recombination reacts effectively with O2(a1Δ) and O atoms. The reaction O3(υ) + O2(a1Δ) O + 2O2 results in a reduction of the ozone recovery rate due to O atom regeneration, whereas the reaction O3(υ) + O 2O2 removes two odd oxygen species, resulting in incomplete ozone recovery. The possible impact of these reactions on the atmospheric O2(a1Δ) and O3 budgets at altitudes in the range of 80–100 km is considered.