Spectroscopic studies of non-volatile residue formed by photochemistry of solid C₄N₂: A model of condensed aerosol formation on Titan

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• 作者：Isabelle Couturier-Tamburelli^a ; ^{isabelle.couturier@univ-amu.fr" class="auth_mail} ; Murthy S. Gudipati^b ; ^{gudipati@jpl.nasa.gov" class="auth_mail} ; Antti Lignell^b ; ^c ; Ronen Jacovi^b ; ^d ; Nathalie Pié ; tri^a
• 关键词：Titan ; Astrobiology ; Ices ; IR Spectroscopy ; Photochemistry ; Prebiotic environments
• 刊名：Icarus
• 出版年：15 May, 2014
• 年：2014
• 卷：234
• 期：Complete
• 页码：81-90
• 全文大小：1561 K

文摘

Following our recent communication (Gudipati, M.S. et al. [2013]. Nat. Commun. 4, 1648. ) on the discovery of condensed-phase non-volatile polymeric material with similar spectral features as tholins, we present here a comprehensive spectroscopic study of photochemical formation of polymeric material from condensed dicyanoacetylene (C₄N₂) ice films. C₄N₂ is chosen as starting material for the laboratory simulations because of the detection of this and similar molecules (nitriles and cyanoacetylenes) in Titan鈥檚 atmosphere. UV-Vis and infrared spectra obtained during long-wavelength (>300 nm) photon irradiation and subsequent warming of the ice films are used to analyze changes in C₄N₂ ice, evolution of tholins, and derive photopolymerization mechanisms. Our data analysis revealed that many processes occur during the photolysis of condensed Titan鈥檚 aerosol analogs, including isomerization and polymerization leading to the formation of long-chain as well as aromatic cyclic polymer molecules. In the light of tremendous new data from the Cassini mission on the seasonal variations in Titan鈥檚 atmosphere, our laboratory study and its results provide fresh insight into the formation and evolution of aerosols and haze in Titan鈥檚 atmosphere.