title: Kinetic measurements on methylidyne radical reactions with several hydrocarbons at low temperatures.
abstract: The temperature dependences of the methylidyne radical reactions with methane, allene, methylacetylene and propene were studied. This work was carried out in a supersonic flow reactor coupled with pulsed laser photolysis (PLP) and laser-induced fluorescence (LIF) techniques. Three Laval nozzles were designed to provide uniform supersonic expansions of nitrogen at Mach 2 and of argon at Mach 2 and 3 to reach low temperatures, e.g. 170, 128 and 77 K, respectively. CH radicals were produced by PLP of CHBr3 at 266 nm and probed by LIF. The exponential decays of the CH fluorescence were acquired, hydrocarbons being introduced in excess. The rate constants for the CH+CH4 reaction are in good agreement with the temperature dependence proposed by Canosa et al. (A. Canosa, I. R. Sims, D. Travers, I. W. M. Smith and B. R. Rowe, Astron. Astrophys., 1997, 323, 644-651, ) i.e. 3.96x10(-8)(T/K)(-1.04) exp(-36.1 K/T) in the range 23-298 K. The rate constants of the CH+C3H4(allene), CH+C3H4(methylacetylene) and CH+C3H6(propene) reactions exhibit a small temperature dependence between 77 and 170 K, with a maximum rate around 100 K close to (4.3-4.6)x10(-10) cm3 molecule-1 s-1.
authors.affiliation: Laboratoire de Physico-Chimie Moléculaire, CNRS UMR5803, Université Bordeaux 1, F-33405, Talence Cedex, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Daugey
authors.forename: Philippe
authors.initials: P
authors.lastname: Caubet
authors.forename: Bertrand
authors.initials: B
authors.lastname: Retail
authors.forename: Michel
authors.initials: M
authors.lastname: Costes
authors.forename: Astrid
authors.initials: A
authors.lastname: Bergeat
authors.forename: Gérard
authors.initials: G
authors.lastname: Dorthe
mesh_terms: D000466:Alkadienes / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D000480:Alkynes / Q000737:chemistry; D001128:Argon / Q000737:chemistry; D003080:Cold Temperature; D005609:Free Radicals / Q000737:chemistry*; D006838:Hydrocarbons / Q000737:chemistry*; D006842:Hydrocarbons, Brominated / Q000737:chemistry; D007700:Kinetics; D007834:Lasers; D008697:Methane / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D010782:Photolysis; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D000466:Alkadienes; D000475:Alkenes; D000480:Alkynes; D005609:Free Radicals; D006838:Hydrocarbons; D006842:Hydrocarbons, Brominated; C022030:methylacetylene; C025947:propadiene; D001128:Argon; C005218:methyl bromide; C013658:propylene; D009584:Nitrogen; D008697:Methane