title: Temperature-dependent branching ratios of deuterated methoxy radicals (CH2DO•) reacting with O2.
abstract: The methoxy radical is an intermediate in the atmospheric oxidation of methane, and the branching ratio (k(1a)/k(1b)) (CH(2)DO• + O(2) → CHDO + HO(2) (1a) and CH(2)DO• + O(2) → CH(2)O + DO(2) (1b)) strongly influences the HD/H(2) ratio in the atmosphere, which is widely used to investigate the global cycling of molecular hydrogen. By using the FT-IR smog chamber technique, we measured the yields of CH(2)O and CHDO from the reaction at 250-333 K. Kinetic modeling was used to confirm the suppression of secondary chemistry. The resulting branching ratios are well fit by an Arrhenius expression: ln(k(1a)/k(1b)) = (416 ± 152)/T + (0.52 ± 0.53), which agrees with the room-temperature results reported in the only previous study. The present results will be used to test our theoretical understanding of the role of tunneling in the methoxy + O(2) reaction, which is the prototype for the entire class of alkoxy + O(2) reactions.
authors.affiliation: Chemistry Department, College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210, United States.
authors.forename: Hongyi
authors.initials: H
authors.lastname: Hu
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Dibble
authors.forename: Geoffrey S
authors.initials: GS
authors.lastname: Tyndall
authors.forename: John J
authors.initials: JJ
authors.lastname: Orlando
mesh_terms: D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D008697:Methane / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013696:Temperature
chemical_list: D005609:Free Radicals; D008697:Methane; D010100:Oxygen