Collisional removal of OH(X2Π,υ= 9) by O, O2, O3, N2, and CO2

Abstract

[1] Total removal rate constants of OH(υ = 9) by O atoms, O2, O3, N2, and CO2 were measured at room temperature. Ozone photodissociation at 248 nm in a mixture containing H2 generates O atoms and OH(υ = 9) by the secondary reaction of H atoms with excess O3. Steady state OH(υ = 9) population measurements using laser-induced fluorescence (LIF) determine the relative rate constants for OH(υ = 9) removal by other species present in the gas mixture. Using available measurements of the absolute removal rate constants by O3 and CO2, we extract a value of (4 ± 1) × 10−10 cm3s−1 (2σ) for the OH(υ = 9) + O rate constant. Collisional removal by O2 and N2 is approximately 20 and 600 times slower, respectively. The result for OH(υ = 9) + O indicates that fast O-atom processes play an important role in determining the OH emission and chemical heating rates in the middle terrestrial atmosphere.