Simulations de laboratoire de la photodynamique VUV de l’atmosphère de Titan

Abstract : Titan, Saturn's biggest satellite, possesses a dense atmosphere, mainly composed of nitrogen (N2) and methane (CH4), which goes up to 1500 km in altitude. The interaction between those chemical species and the solar light leads to some photodissociation and photoionization reactions that are the starting point of a fast and efficient molecular growth in the upper layers of the atmosphere. This growth ends with the synthesis of aerosols around an altitude of 1000 km that will then precipitate into the atmosphere.The aim of this thesis is to experimentally study the interaction between the species present in the upper atmosphere and the energetic solar radiations in the vacuum ultraviolet (VUV) range (wavelength below 150 nm). First, we looked at the interaction with the small, neutral and most abundant species thanks to a new VUV source specially designed for this thesis and coupled to photochemical reactor called APSIS. This new platform sheds some light on the photochemistry of a coupled nitrogen-methane system, which remains poorly understood.Then, we focused on the effects of the VUV light on the aerosols formed in the upper layers, by photoionizing, with synchrotron light from the DESIRS beamline, analogs of those aerosols produced on the PAMPRE platform. This method gives information about their photoionization (threshold and cross sections, photoelectron spectra) but also about their optical properties.
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Submitted on : Thursday, February 22, 2018 - 10:16:08 AM
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  • HAL Id : tel-01663469, version 2

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Sarah Tigrine. Simulations de laboratoire de la photodynamique VUV de l’atmosphère de Titan. Astrophysique [astro-ph]. Université Paris-Saclay, 2017. Français. ⟨NNT : 2017SACLV060⟩. ⟨tel-01663469v2⟩

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