Atmospheric deuterium fractionation: HCHO and HCDO yields in the CH2DO + O2 reaction E. J. K. Nilsson1, M. S. Johnson1, F. Taketani2, Y. Matsumi2, M. D. Hurley3, and T. J. Wallington3 1Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark 2Solar-Terrestrial Environment Laboratory and Graduate School of Science, Nagoya University 3-13 Hohohara, Toyokawa, Aichi 442-8507, Japan 3Research and Innovation Center, Ford Motor Company, Dearborn MI 48121-2053, USA
Abstract. The formation of formaldehyde via hydrogen atom transfer from the methoxy
radical to molecular oxygen is a key step in the atmospheric photochemical
oxidation of methane, and in the propagation of deuterium from methane to
molecular hydrogen. We report the results of the first investigation of the
branching ratio for HCHO and HCDO formation in the CH2DO + O2
reaction. Labeled methoxy radicals (CH2DO) were generated in a
photochemical reactor by photolysis of CH2DONO. HCHO and HCDO
concentrations were measured using FTIR spectroscopy. Significant deuterium
enrichment was seen in the formaldehyde product, from which we derive a
branching ratio of 88.2±1.1% for HCDO and 11.8±1.1% for
HCHO. The implications of this fractionation on the propagation of deuterium
in the atmosphere are discussed.
Citation: Nilsson, E. J. K., Johnson, M. S., Taketani, F., Matsumi, Y., Hurley, M. D., and Wallington, T. J.: Atmospheric deuterium fractionation: HCHO and HCDO yields in the CH2DO + O2 reaction, Atmos. Chem. Phys., 7, 5873-5881, doi:10.5194/acp-7-5873-2007, 2007.