On an EUV Atmospheric Simulation Chamber to Study the Photochemical Processes of Titan’s Atmosphere

Abstract

the in situ exploration of titan's atmosphere requires the development of laboratory experiments to understand the molecular growth pathways initiated by photochemistry in the upper layers of the atmosphere. Key species and dominant reaction pathways are used to feed chemical network models that reproduce the chemical and physical processes of this complex environment. energetic UV photons initiate highly efficient chemistry by forming reactive species in the ionospheres of the satellite. We present here a laboratory experiment based on a new closed and removable photoreactor coupled here to an extreme Ultraviolet (eUV) irradiation beam produced by the high-order harmonic generation of a femtosecond laser. this type of eUV stable source allow long-term irradiation experiments in which a plethora of individual reactions can take place. in order to demonstrate the validity of our approach, we irradiated for 7 hours at 89.2 nm, a gas mixture based on N 2 /cH 4 (5%). Using only one wavelength, products of the reaction reveal an efficient photochemistry with the formation of large hydrocarbons but especially organic compounds rich in nitrogen similar to titan. Among these nitrogen compounds, new species had never before been identified in the mass spectra obtained in situ in titan's atmosphere. their production in this experiment, on the opposite, corroborates previous experimental measurements in the literature on the chemical composition of aerosol analogues produced in the laboratory. Diazo-compounds such as dimethyldiazene (c 2 H 6 n 2), have been observed and are consistent with the large nitrogen incorporation observed by the aerosols collector pyrolysis instrument of the Huygens probe. this work represents an important step forward in the use of a closed cell chamber irradiated by the innovative eUV source for the generation of photochemical analogues of titan aerosols. this approach allows to better constrain and understand the growth pathways of nitrogen incorporation into organic aerosols in titan's atmosphere.

Aromatic Formation Promoted by Ion-Driven Radical Pathways in EUV Photochemical Experiments Simulating Titan’s Atmospheric Chemistry

“…The experimental setup has already been described in the literature, and thus, only the specificities related to this study are described in this section . Each part of the reactor was cleaned with ethanol before assembly and the reactor was then pumped to a secondary vacuum and heated for 48 h at a temperature sufficient to minimize the contribution of water vapor and organic pollutants whose presence is checked before each irradiation.…”

“…The signal of each mass may result from a contribution of several fragments coming from parent molecules. As mentioned in Bourgalais et al, the National Institute of Standards and Technology (NIST) () fragmentation database has been used as a reference for the fragmentation patterns involved here.…”

“…To achieve that, the recently developed atmospheric simulation chamber SURFACAT (french acronym for surfatron chambre à tholins ) has been used . This new experimental platform has been coupled to the EUV light source of the BlastBeat laser system at the CELIA laboratory in Bordeaux, France .…”

“…This new experimental platform has been coupled to the EUV light source of the BlastBeat laser system at the CELIA laboratory in Bordeaux, France . The feasibility of irradiating for several hours a low pressure gas sample in the SURFACAT reactor to form photoproducts using a stable EUV photon flux was recently presented in Bourgalais et al This paper presents a first series of results relating to the study of Titan’s chemistry through the use of an experimental device with a low level of contamination. The paper is organized as follows.…”

Aurore: A platform for ultrafast sciences

“…Indeed, HHG sources possess a number of properties that make them ideal for many applications: excellent spatial coherence 18 , high brightness (above 10 10 photons per pulse using energetic Ti:Sapphire laser pulses 19,20 , above 10 13 photons per second using high-repetition rate Ytterbium fiber lasers 21,22 ), and ultrashort duration (femtosecond 23,24 and attosecond [25][26][27] pulses). These properties make HHG sources appealing for timeresolved measurements in atomic, molecular, and solidstate physics, but also as a simple alternative Vacuum UltraViolet source of irradiation to investigate laboratory astrochemistry, for instance 28 .…”