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[5.08] Photochemistry of C2H2, C2H4 and HC3N at 185 nm. Applications to Titan’s atmospheric chemistry

B. Tran (Rensselaer Polytechnic Institute), M. Force, R. Briggs (NY State Department of Health), V. Vuitton, J. Ferris (Rensselaer Polytechnic Institute)

The irradiation of a gaseous mixture that simulates Titan’s atmosphere (N2, CH4, H2, C2H2, C2H4, and HC3N) in a flow reactor using a lamp emitting 185 and 254 nm light generates a solid (a Titan haze analog) and over 180 volatile reaction products. The structures of many of these products have been determined by GC/MS analysis. The reaction pathways were investigated by irradiation of the individual reactants (C2H2, and C2H4) alone and in the presence of CH4. Photolysis of C2H2 yields mainly C4H2 and small amounts of aromatic hydrocarbons while C2H4 yields mainly saturated hydrocarbons like propane, butane and pentane. Irradiation of HC3N yields HCN, CH3CN and C2H5CN (Clarke et al. 2000). Irradiation of 13C2H2 labels those products formed from C2H2. The quantum yields for reactant loss and product formation were determined and will be used for the generation of a model for the photochemical processes. The products are likely constituents of Titan’s atmosphere and their structures will provide insight into the structure of Titan’s haze.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.