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Laboratory experiments as support to the built up of Titan's theoretical models and interpretation of Cassini-Huygens data

Published online by Cambridge University Press:  01 February 2008

Marie-Claire Gazeau
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Yves Benilan
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Et Touhami Es-sebbar
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Thomas Ferradaz
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Eric Hébrard
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Antoine Jolly
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
François Raulin
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Claire Romanzin
Affiliation:
LISA (Laboratoire Interuniversitaire des Systèmes atmosphériques), groupe de Physico-chimie Organique Spatiale, UMR CNRS 7583, Universités Paris 12 et Paris 7, Créteil, 94010, France email: gazeau@lisa.univ-paris12.fr
Jean-Claude Guillemin
Affiliation:
Sciences chimiques de Rennes, UMR 6226 CNRS-Ecole Nationale Supérieure de Chimie de Rennes, Rennes, F-35700, France
Coralie Berteloite
Affiliation:
Équipe d'Astrochimie Expérimentale, Université de Rennes 1, France
André Canosa
Affiliation:
Équipe d'Astrochimie Expérimentale, Université de Rennes 1, France
Sébastien D. Le Picard
Affiliation:
Équipe d'Astrochimie Expérimentale, Université de Rennes 1, France
Ian R. Sims
Affiliation:
Équipe d'Astrochimie Expérimentale, Université de Rennes 1, France
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Abstract

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To interpret the concentrations of the products measured in Titan's atmosphere and to better understand the associated chemistry, many theoretical models have been developed so far. Unfortunately, large discrepancies are still found between theoretical and observational data. A critical examination of the chemical scheme included in these models points out some problems regarding the reliability of the description of critical reaction pathways as well as the accuracy of kinetic parameters. Laboratory experiments can be used to reduce these two sources of uncertainty. It can be:

i) experimental simulations: in our laboratory (LISA), representative Titan's simulation experiments are planned to be carried out in a reactor where the initial gas mixture will be exposed, for the first time, to both electrons and photons. Thus, the chemistry between N atoms and CH3, CH2, CH fragments, issued from electron dissociation of N2 and photo-dissociation of CH4 respectively, will be initiated. Thank to a time resolved technique, we will be able to analyse “in situ”, qualitatively and quantitatively, the stable species as well as the short life intermediates. Then, the implied chemistry will be determined precisely, and consequently, its description will be refined in theoretical models. The current status of this program will be given.

ii) specific experiments: they are devoted, for example, to determine kinetic rate constants and low temperature VUV spectra that will be used to feed models and to interpret observational data. Such experiments performed in LISA and in Rennes' laboratory concern polyynes and cyanopolyynes as these compounds could link the gaseous and the solid phase in planetary atmosphere. Results concerning C4H+ hydrocarbons kinetic rate constants and VUV cross section of HC3N and HC5N will be detailed.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2008