INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Direct measurement of the rate constant for the reaction of CH3O2 radicals with OH radicals
Autor/es:
ADRIANA G. BOSSOLASCO; ESZTER P. FARAGÓA; CORALIE SCHOEMAECKER; CHRISTA FITTSCHEN
Lugar:
Szeged
Reunión:
Simposio; 23rd International Symposium on Gas Kinetics; 2014
Resumen:
Peroxy alkyl radicals (RO2) are key reaction intermediates in the low temperature oxidation of organic compounds and play a central role in atmospheric chemistry. They are predominantly formed from the initial reaction of OH radicals with hydrocarbons, leading to formation of an alkyl radical R: RH + OH --> R + H2O followed by recombination of the alkyl radical with molecular oxygen R + O2 --> RO2 In polluted environments, peroxy radicals react predominantly with NO, leading to formation of NO2, which through subsequent photolysis leads to formation of O3. At low NOx concentrations such as in the remote continental boundary layer, the marine boundary layer, and the background troposphere, the lifetime of RO2 radicals increases and other reaction pathways become competitive for peroxy radicals. Atmospheric chemistry models consider self- and cross reactions with other RO2 radicals or with HO2 radicals as the major fate for RO2 radicals under these conditions, in the example of CH3O2: CH3O2 + CH3O2 --> 2 CH3O + O2 (R1a) --> CH2O + CH3OH + O2 (R1b) CH3O2 + HO2 --> CH3O2H + O2 (R2) Currently, the reaction of RO2 radicals with OH radicals RO2 + OH --> products (R3) is not considered in models, even though if fast enough, it might become competitive with (R1) and (R2). We present the first measurement of the rate constant for the title reaction by coupling laser photolysis to a simultaneous, time resolved detection of CH3O2 radicals by cw-CRDS [1] and OH radicals by high repetition rate LIF. A very fast rate constant of 2.8×10-10 cm3s-1 has been found [2], making this reaction a non-negligible pathway for peroxy radicals under remote conditions. The implications for the chemistry of the atmosphere will be discussed. References [1] Faragó, E. P.; Viskolcz, B.; Schoemaecker, C.; Fittschen, C. Absorption Spectrum and Absolute Absorption Cross Sections of CH3O2 Radicals and CH3I Molecules in the Wavelength Range 7473?7497 cm?1, J. Phys. Chem. A, 117, 12802-12811 (2013) [2] Bossolasco, A.; Faragó, E. P.; Schoemaecker, C.; Fittschen, C. Rate constant of the reaction between CH3O2 and OH radicals. Chem. Phys. Lett., 593, 7-13 (2014)