title: Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich Environments.
abstract: Product detection studies of C(3P) atom reactions with butene (C4H8) isomers (but-1-ene, cis-but-2-ene, trans-but-2-ene) are carried out in a flow tube reactor at 353 K and 4 Torr under multiple collision conditions. Ground state carbon atoms are generated by 248 nm laser photolysis of tetrabromomethane, CBr4, in a buffer of helium. Thermalized reaction products are detected using synchrotron tunable VUV photoionization and time-of-flight mass spectrometry. The temporal profiles of the detected ions are used to discriminate products from side or secondary reactions. For the C(3P) + trans-but-2-ene and C(3P) + cis-but-2-ene reactions, various isomers of C4H5and C5H7are identified as reaction products formed via CH3and H elimination. Assuming equal ionization cross sections for all C4H5and C5H7isomers, C4H5:C5H7branching ratios of 0.63:1 and 0.60:1 are derived for the C(3P) + trans-but-2-ene and the C(3P) + cis-but-2-ene reactions, respectively. For the C(3P) + but-1-ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3+ C2H5channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3radicals, a branching ratio of 1:0.95 for the C3H3+ C2H5and H + ethylpropargyl channels is derived. The experimental results are compared to previous H atom branching ratios and used to propose the most likely mechanisms for the reaction of ground state carbon atoms with butene isomers.
authors: Institut de Physique de Rennes, Département de Physique Moléculaire, Astrophysique de Laboratoire, UMR CNRS 6251, Université de Rennes 1 , Campus de Beaulieu, 35042 Rennes Cedex, France.
authors: J
authors: J
authors: Bourgalais
authors: Department of Chemistry, West Virginia University , Morgantown, West Virginia 26506, United States.
authors: Michael
authors: M
authors: Spencer
authors: Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories , Livermore, California 94551, United States.
authors: David L
authors: DL
authors: Osborn
authors: Department of Chemistry, West Virginia University , Morgantown, West Virginia 26506, United States.
authors: F
authors: F
authors: Goulay
authors: Institut de Physique de Rennes, Département de Physique Moléculaire, Astrophysique de Laboratoire, UMR CNRS 6251, Université de Rennes 1 , Campus de Beaulieu, 35042 Rennes Cedex, France.
authors: S D
authors: SD
authors: Le Picard