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

Total removal rate constants of OH(upsilon = 9) by O atoms, O-2, O-3, N-2, and CO2 were measured at room temperature. Ozone photodissociation at 248 nm in a mixture containing H-2 generates O atoms and OH(upsilon = 9) by the secondary reaction of H atoms with excess O-3. Steady state OH(upsilon = 9) population measurements using laser-induced fluorescence (LIF) determine the relative rate constants for OH(upsilon = 9) removal by other species present in the gas mixture. Using available measurements of the absolute removal rate constants by O-3 and CO2, we extract a value of (4 +/- 1) x 10(-10) cm(3)s(-1) (2 sigma) for the OH(upsilon = 9) + O rate constant. Collisional removal by O-2 and N-2 is approximately 20 and 600 times slower, respectively. The result for OH(upsilon = 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.