Kinetics and branching ratio studies of the reaction of C2H 5O2 + HO2 using chemical ionisation mass spectrometry

M. Teresa Raventós-Duran, Carl J. Percival, Max R. McGillen, Paul D. Hamer, Dudley E. Shallcross

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The overall rate coefficient for the reaction of C2H 5O2 with HO2 was determined using a turbulent flow chemical ionization mass spectrometer (TF-CIMS) system over the pressure range of 75 to 200 Torr and temperatures between 195 and 298 K. The temperature dependence of the overall rate coefficient for the reaction between C 2H5O2 and HO2 was fitted using the following Arrhenius expression: k(T) = (2.08-0.62+0.87) × 10-13 exp [(864 ± 79)/T] cm-3 molecule -1 s-1. The upper limits for the branching ratios for reactive channels leading to O3 and OH production were quantified for the first time. A tropospheric model has been used to assess the impact of the experimental error of the rate coefficients determined in this study on predicted concentrations of a number of key species, including O3, OH, HO2, NO and NO2. In all cases it is found that the propagated error is very small and will not in itself be a major cause of uncertainty in modelled concentrations. However, at low temperatures, where there is a wide discrepancy between existing kinetic studies, modelling using the range of kinetic data in the literature shows a small but significant variation for [C2H5O2], [C2H 5OOH], [NOx] and the HO2:OH ratio. Furthermore, a structure-activity relationship (SAR) was developed to rationalise the reactivity of the reaction between RO2 and HO2. © the Owner Societies.
    Original languageEnglish
    Pages (from-to)4338-4348
    Number of pages10
    JournalPhysical Chemistry Chemical Physics
    Volume9
    Issue number31
    DOIs
    Publication statusPublished - 2007

    Keywords

    • ORGANIC PEROXY-RADICALS
    • SELF-REACTION
    • GAS-PHASE
    • PRESSURE-DEPENDENCE
    • RATE CONSTANTS
    • ABSORPTION-SPECTROSCOPY
    • ATMOSPHERIC CHEMISTRY
    • BOUNDARY-LAYER
    • PRODUCT YIELD
    • HO2

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