Laboratory experiments for Titan's ionosphere : the chemistry of N2+, N+, and N2++ nitrogen ions

Roland Thissen (1) , Christian Alcaraz (1) , Odile Dutuit (1) , C. Nicolas (2) , H. Soldi-Lose (3) , Jan Zabka (4) , P. Francheschi (5)

1 LCPO - Laboratoire de Chimie Physique D'Orsay
2 SSOLEIL - Synchrotron SOLEIL
3 Institut für Chemie
4 J. Heyrovský Institute of Physical Chemistry
5 Dept. of Physics

N2 is the major neutral componant of Titan's atmosphere, its ionisation by solar radiation and by magnetospheric electron impact is the most important production of ions in Titan's ionosphere. These primary processes not only lead to N+ 2 molecular monocations but also to N+ atomic ions and to N2+ 2 molecular dications, which can pertain some internal or translational excitation. This contribution will summarize our efforts to caracterize in gaz phase laboratory experiments the reactivity of the nitrogen ions with the most important neutral targets of the Titan's atmosphere [1-3]: • N+ 2 + CH4, C2H2, and C2H6 • N+(3P, 1D) + CH4, and C2H4 • N2+ 2 + N2, CH4, and C2H4 In this work, particular attention has been paid on the effect of internal and/or translational excitation of the primary nitrogen ions on the rate constant and branching ratio of these ion-molecule reactions. The results from these studies have been compared to the literature values when available and some significant differences have been found. These new values have been used as input data in 1D models of the Titan's ionosphere to show the effect on the final density profiles of the main ions [4] and to demonstrate the existence of a N2+ 2 dication layer [3].

Roland Thissen, Christian Alcaraz, Odile Dutuit, C. Nicolas, H. Soldi-Lose, et al.. Laboratory experiments for Titan's ionosphere : the chemistry of N2+, N+, and N2++ nitrogen ions. European Planetary Science Congress 2006, 2006, Berlin, Germany. ⟨insu-00358080⟩