Kinetics of the cross-reaction of CH3O2 + HO2 radicals measured in the Highly Instrumented Reactor for Atmospheric Chemistry

Freja F. Østerstrøm, Lavinia Onel, Alexander Brennan, Joseph M. Parr, Lisa K. Whalley, Paul W. Seakins, Dwayne E. Heard

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The sensitive Fluorescence Assay by Gas Expansion (FAGE) method has been used to detect methyl peroxy (CH3O2) and hydroperoxyl (HO2) radicals after their conversion by titration with excess NO to methoxy (CH3O) and hydroxyl (OH) radicals, respectively, to study the kinetics of the reaction of CH3O2 + HO2 radicals. The rate coefficient of the reaction was measured in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) at 1000 mbar of synthetic air at T = 268–344 K, selectively detecting both radicals. Using a numerical model to fit both CH3O2 and HO2 radical temporal decays globally at each temperature investigated, rate coefficients for the reaction have been obtained. The room temperature rate coefficient was found to be kCH3O2 +HO2(295 K) = (4.6 ± 0.7) × 10−12 molecule−1 cm3 s−1 (2σ errors) and the temperature dependence of the rate coefficient can be characterized in Arrhenius form by kCH3O2 + HO2(268 K < T < 344 K) = (5.1 ± 2.1) × 10−13 × exp((637 ± 121)/T) cm3 molecule−1 s−1. The rate coefficients obtained here are 14%–16% lower than the literature recommended values with an uncertainty which is reduced significantly compared to previous reports.

Original languageEnglish
Pages (from-to)489-500
Number of pages12
JournalInternational Journal of Chemical Kinetics
Volume55
Issue number8
DOIs
Publication statusPublished - Aug 2023
Externally publishedYes

Keywords

  • gas phase reactions
  • global fitting
  • kinetics
  • radical-radical reactions
  • temperature dependence

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