31st Annual Meeting of the DPS, October 1999
Session 45. Titan: Chemistry
Contributed Oral Parallel Session, Thursday, October 14, 1999, 10:30-11:50am, Sala Pietro d'Abano

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[45.07] Complex Refractive Index of Titan's Aerosol Analogues (in the 200-1000 nm Range)

P. Coll (LISA - CNRS, Universities of Paris 7 and Paris 12 - France), S. I. Ramirez (LQPEP - ICN - UNAM - Mexico), A. Da Silva, J. Lafait (LOS - University of Paris 6 - France), R. Navarro-Gonzalez (LQPEP - ICN - UNAM - Mexico), F. Raulin (LISA - CNRS, Universities of Paris 7 and Paris 12 - France)

Chemistry taking place in the upper atmosphere of Titan evolve to the production of heavier C-H-N organic compounds who form the particles of the haze layers that hide Titan's surface. Among the parameters involved in the different physical models, the complex refractive index of Titan's aerosols is one of the most critical due to the influence that the chemical composition and structural organization has on its parameters. It is therefore useful to have a correct estimation of their values. The first laboratory experiment was carried out by Khare et al. (1984) where they determined these parameters for a product supposed to be a material that well reproduced the Titan's aerosols. It has to be appreciated the effort of Sagan group in performing these measurements, but it has to be also recognized that the fitted values can carry a great uncertainty. Nevertheless, these results have been used during fifteen years by several investigators and have formed the basis for a long series of calculations and photochemical models, even when a correction factor is always necessary to accomplish a good fit of the data. In the frame of a program for getting characteristics of Titan's aerosol analogues, measurements of the complex refractive index were done (Coll et al., 1999). The results showed no relationship with previous studies, and made us to establish a protocol to initiate a detailed study of these optical characteristics of analogues produced under more realistic and well controlled conditions. Finally we present here sets of graphics for transmission, reflectance, and final determinations of refractive index and extinction coefficient with error bars, assuming thickness uncertainties and porosity effects modeling. Critical reading of these graphs will be exposed (how the optical properties of these aerosols can influence the matching of the observed geometric albedo spectrum...).

The author(s) of this abstract have provided an email address for comments about the abstract: coll@lisa.univ-paris12.fr

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