Reactions of Atomic Carbon with Butene Isomers: Implications for Molecular Growth in Carbon-Rich EnvironmentsReport as inadecuate

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* Corresponding author 1 IPR - Institut de Physique de Rennes 2 West Virginia University Morgantown 3 Combustion Research Facility

Abstract : Product detection studies of CP-3 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 CP-3 + trans-but-2-ene and CP-3 + cis-but-2-ene reactions, various isomers of C4H5 and C5H7 are identified as reaction products formed via CH3 and H elimination. Assuming equal ionization cross sections for all C4H5 and C5H7 isomers, C4H5:C5H7 branching ratios the CP-3 + trans-but-2-ene and the C3P + cis-but-2-ene reactions, respectively. For the CP-3 + but-1-ene reaction, two reaction channels are observed: the H-elimination channel, leading to the formation of the ethylpropargyl isomer, and the C3H3 + C2H5 channel. Assuming equal ionization cross sections for ethylpropargyl and C3H3 radicals, a branching ratio of 1:0.95 for the C3H3 + C2H5 and 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.

Keywords : crossed-beam reaction resonance-absorption spectroscopy product branching ratios vacuum ultra-violet titans atmosphere rate coefficients hydrocarbon molecules interstellar-medium chemical-dynamics ab-initio

Author: Jérémy Bourgalais - Michael Spencer - David L. Osborn - Fabien Goulay - Sébastien Le Picard -



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