title: Low temperature rate coefficients for reactions of the butadiynyl radical, C4H, with various hydrocarbons. Part I: reactions with alkanes (CH4, C2H6, C3H8, C4H10).
abstract: The kinetics of the reactions of the linear butadiynyl radical, C4H (CCCCH), with methane, ethane, propane and butane have been studied over the temperature range of 39-300 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. The rate coefficients, except for the reaction with methane, show a negative temperature dependence and can be fitted with the following expressions over the temperature range of this study: k(C2H6) = 0.289 x 10(-10) (T/298 K)(-1.23) exp(-24.8 K/T) cm3 molecule(-1) s(-1); k(C3H8) = 1.06 x 10(-10) (T/298 K)(-1.36) exp(-56.9 K/T) cm3 molecule(-1) s(-1); k(C4H10) = 2.93 x 10(-10) (T/298 K)(-1.30) exp(-90.1 K/T) cm3 molecule(-1) s(-1). The rate coefficients for the reaction with methane were measured only at 200 K and 300 K yielding a positive temperature dependence: k(CH4) = 1.63 x 10(-11) exp(-610 K/T) cm3 molecule(-1) s(-1). Possible reaction mechanisms and product channels are discussed in detail for each of these reactions. Potential implications of these results for models of low temperature chemical environments, in particular cold interstellar clouds and planetary atmospheres such as that of Titan, are considered.
authors.affiliation: Institut de Physique de Rennes, Equipe Astrochimie Expérimentale UMR 6251 du CNRS-Université de Rennes 1, Bât. 11c, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Coralie
authors.initials: C
authors.lastname: Berteloite
authors.forename: Sébastien D
authors.initials: SD
authors.lastname: Le Picard
authors.forename: Nadia
authors.initials: N
authors.lastname: Balucani
authors.forename: André
authors.initials: A
authors.lastname: Canosa
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sims