title: Kinetics of CH2OO reactions with SO2, NO2, NO, H2O and CH3CHO as a function of pressure.
abstract: Kinetics of CH2OO Criegee intermediate reactions with SO2, NO2, NO, H2O and CH3CHO and CH2I radical reactions with NO2 are reported as a function of pressure at 295 K. Measurements were made under pseudo-first-order conditions using flash photolysis of CH2I2-O2-N2 gas mixtures in the presence of excess co-reagent combined with monitoring of HCHO reaction products by laser-induced fluorescence (LIF) spectroscopy and, for the reaction with SO2, direct detection of CH2OO by photoionisation mass spectrometry (PIMS). Rate coefficients for CH2OO + SO2 and CH2OO + NO2 are independent of pressure in the ranges studied and are (3.42 ± 0.42) × 10(-11) cm(3) s(-1) (measured between 1.5 and 450 Torr) and (1.5 ± 0.5) × 10(-12) cm(3) s(-1) (measured between 25 and 300 Torr), respectively. The rate coefficient for CH2OO + CH3CHO is pressure dependent, with the yield of HCHO decreasing with increasing pressure. Upper limits of 2 × 10(-13) cm(3) s(-1) and 9 × 10(-17) cm(3) s(-1) are placed on the rate coefficients for CH2OO + NO and CH2OO + H2O, respectively. The upper limit for the rate coefficient for CH2OO + H2O is significantly lower than has been reported previously, with consequences for modelling of atmospheric impacts of CH2OO chemistry.
authors.affiliation: School of Chemistry, University of Leeds, Leeds, UK. m.blitz@leeds.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Stone
authors.forename: Mark
authors.initials: M
authors.lastname: Blitz
authors.forename: Laura
authors.initials: L
authors.lastname: Daubney
authors.forename: Neil U M
authors.initials: NU
authors.lastname: Howes
authors.forename: Paul
authors.initials: P
authors.lastname: Seakins
mesh_terms: D000079:Acetaldehyde / Q000737:chemistry*; D007700:Kinetics; D009569:Nitric Oxide / Q000737:chemistry; D009585:Nitrogen Dioxide / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D011312:Pressure; D013458:Sulfur Dioxide / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D010087:Oxides; D014867:Water; D013458:Sulfur Dioxide; D009569:Nitric Oxide; D000079:Acetaldehyde; D009585:Nitrogen Dioxide