Is the Reaction Rate Coefficient for OH + HO2 → H2O + O2 Dependent on Water Vapor?
Year: 2024
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide A critical reaction affecting the oxidation chemistry in the middle-to-upper atmosphere occurs between hydroxyl (OH) and hydroperoxyl (HO 2 ). The reaction rate coefficient for OH + HO 2 → H 2 O + O 2, here called k OH+HO2, has challenged laboratory kineticists for 50 years. However, several measurements from the past 30 years had approached a rough consensus until the publication of a new study that examined, for the first time, the water vapor dependence of this reaction. According to the study, k OH+HO2 is not the recommended value of 11.0 × 10 –11 cm 3 molecule –1 s –1, but instead, a water-dependent (∼1 × 10 –11 + 2.17 × 10 –28 [H 2 O]) cm 3 molecule –1 s –1 . Our study examines the water dependence of k OH+HO2 using water vapor photolysis of moist air at atmospheric pressure in a flow tube, with direct detection of both OH and HO 2 . The observed OH decays were due only to the OH reaction with HO 2 and, to a lesser extent, the OH loss to the flow tube wall and trace impurities. The resulting k OH+HO2 is (8.54 ± 2.90) × 10 –11 cm 3 molecule –1 s –1, 68% confidence, independent of water vapor and lower than but consistent with the recommended value.
Source: JACS Au
Authors: William H. Brune, Jena M. Jenkins
Institution: Pennsylvania State University
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,500
OpenAlex ID: W4404611007