Crossed molecular beam study of gas phase reactions relevant to the chemistry of planetary atmospheres: The case of C2+C2H2

Year: 2008

Authors: Leonori F., Petrucci R., Hickson K. M., Segoloni E., Balucani N., Le Picard S.D., Foggi P., Casavecchia P.

Autors Affiliation: Dipartimento di Chimica, Universita` di Perugia, 06123 Perugia, Italy

Abstract: The reaction between dicarbon (C2) and acetylene was recently suggested as a possible competitive reaction in the atmospheres of Titan, Saturn and Uranus by rate constant measurements at very low temperatures [see Canosa, A., Páramo, A., Le Picard, S.D., Sims, I.R., 2007. An experimental study of the reaction kinetics of C2(X1Σg+) with hydrocarbons (CH4, C2H2, C2H4, C2H6 and C3H8) over the temperature range 24–300 K: implications for the atmospheres of Titan and the Giant Planets. Icarus 187, 558–568]. We have investigated the reaction of the two low lying electron states of C2 and acetylene by the crossed molecular beam (CMB) technique with mass spectrometric detection. C4H, already identified as a primary product in previous CMB experiments, is confirmed as such, even though the mechanism of formation is inferred to be partly different with respect to the previous study. An experimental setup has been devised to characterize the internal population of C2 and refine the interpretation of the scattering results. The implications for the modelling of the atmospheres of Giant Planets and Titan, as well as cometary comae and the interstellar medium, are discussed.

Journal/Review: PLANETARY AND SPACE SCIENCE

Volume: 56 (12)      Pages from: 1658  to: 1673

More Information: Faculty of Science and Engineering, University of Manchester, FSE. Lavoro. European Commission, EC. MCRTN-CT-2004-512302. 001637. – We acknowledge financial support by the Italian MIUR (PRIN 2005) and the European Commission through the Coordination Action 001637 (Europlanet). This work is also supported by the European Union Marie-Curie human resources and mobility programme, including post-doctoral fellowship for K.M. Hickson, under Contract MCRTN-CT-2004-512302 (Molecular Universe). We thank P. Sharkey, A. Paladini, R. Cireasa, M. Pasquini and R. Piani for their contribution in setting up the LIF system and E.B. Jochnowitz for help in the spectra simulations of C 2 . R. Petrucci thanks FSE (Fondo Sociale Europeo)—Regione Umbria—Ministero del Lavoro e delle Politiche Sociali for a fellowship. N. Balucani wishes to thank P. Lavvas for useful discussions.
KeyWords: Acetylene; Experiments; Hydrocarbons; Interplanetary flight; Lighting; Molecular beams; Molecular dynamics; Optical sensors; Organic compounds; Petroleum refining; Planets; Reaction kinetics, Atmospheres; Comets; Composition; Experimental techniques; Jovian planets; Titan, Rate constants
DOI: 10.1016/j.pss.2008.04.011

Citations: 33
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