Kinetic parameters related to sources and sinks of vibrationally excited OH in the nightglow

Abstract

Kinetic parameters related to vibrational deactivation and chemical removal of vibrationally excited OH radicals in the mesosphere are deduced from ground‐based measurements of the mean vibrational distribution of the OH Meinel bands in the nightglow. The derived parameters, which rely on a laboratory measured rate coefficient for the removal of OH(υ = 9) by O 2 (Finlayson‐Pitts and Kleindienst, 1981) and a set of relative Meinel band transition probabilities (Murphy, 1971), have been obtained for two limiting Meinel band excitation models that differ in the extent to which single‐quantum vibrational deactivation and “sudden death” collisional removal processes determine the OH vibrational distribution. It is shown that the OH Meinel band emission can be adequately explained with the deduced parameters and the H + O 3 →OH + O 2 reaction as the only chemical source of vibrationally excited OH. Evidence is presented which suggests that the reaction HO 2 + O ↔ HO + O 2 may perhaps be involved as a sink of vibrationally excited OH rather than as a potential source. The deduced kinetic parameters should be particularly useful in future Meinel band studies as they have been obtained from an analysis for which there is no assumption about the very uncertain OH radiative lifetimes.