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[57.05] Experimental and theoretical, IR and UV, spectra of unsaturated organic molecules: implications for their detection and modeling in methane rich atmospheres.

Y. Benilan, F. Shindo, A. Jolly, V. Vuitton, M.-C. Gazeau (LISA, Universites Paris VII et XII, France), P. Chaquin (LCT, Universite Paris VI, France), J.-C. Guillemin (LCOB, ENSCR, France), F. Raulin (LISA, Universites Paris VII et XII, France)

Unsaturated organic compounds have been observed in the atmosphere of most Giant Planets and Titan. Their production results from the photo-dissociation of methane in the high atmosphere. The higher molecular weight compounds that have been detected, are also the most unsaturated ones: polyynes, cyanopolyynes and di-cyanopolyynes. This suggested that, in methane rich atmospheres, organic aerosols could be formed via the photochemical evolution methane to long carbon chain unsaturated compounds. To test this hypothesis, observational and photochemical modeling works have to be performed in synergy. But, to achieve this task spectroscopic, photochemical and kinetic data are needed in adequate, mainly low temperature, conditions of the studied environments. Since the thermal stability and vapor pressure decrease with the increasing length of unsaturated compounds, required data are difficult to obtained in the laboratory. Consequently, coupled experimental and theoretical works need to be done. We report here IR and UV spectroscopic studies that we have performed on unsaturated compounds: polyynes, cyanopolyynes and di-cyanopolyynes. We will emphasis on the experimental limitations encounter. And, we will show how experimental and theoretical works can be used to drive the search of those compounds in the outer solar system.