Pressure and temperature dependences of rate coefficients for the reaction OH + NO_2 + M → products

Abstract

The OH + NO_2 reaction is a critically important process for radical chain termination in the atm. with a major impact on the ozone budgets of the troposphere and stratosphere. Rate consts. for the reaction of OH + NO_2 + → products have been measured under conditions relevant to the upper troposphere/lower stratosphere with a Pulsed Laser Photolysis - Pulsed Laser Induced Fluorescence technique augmented by in situ optical spectroscopy for quantification of [NO_2]. The expts. are carried out over the temp. range of 230K - 330K and the pressure range 40-800 Torr of air and N_2. The reaction was studied under pseudo first-order conditions, monitoring the decay of OH in the presence of a large excess of NO_2. The obsd. pressure and temp. dependences are analyzed to quantify the falloff behavior and to derive parameters for Troe falloff expressions. The atm. implications are discussed.