title: Molecular Isomer Identification of Titan's Tholins Organic Aerosols by Photoelectron/Photoion Coincidence Spectroscopy Coupled to VUV Synchrotron Radiation.
abstract: The chemical composition of Titan organic haze is poorly known. To address this issue, laboratory analogues named tholins are synthesized and analyzed by methods often requiring an extraction process in a carrier solvent. These methods exclude the analysis of the insoluble tholins' fraction and assume a hypothetical chemical equivalence between soluble and insoluble fractions. In this work, we present a powerful complementary analysis method recently developed on the DESIRS VUV synchrotron beamline at SOLEIL. It involves soft pyrolysis of tholins at ∼230 °C and electron/ion coincidence analysis of the emitted volatile compounds photoionized by tunable synchrotron radiation. By comparison with reference photoelectron spectra (PES), the spectral information collected on the detected molecules yields their isomeric structure. The method is more readily applied to light species (m/z ≤ 69), while for heavier ones, the number of possibilities and the lack of PES reference spectra in the literature limit its analysis. A notable pattern in the analyzed tholins is the presence of species containing adjacent doubly bonded N atoms, which might be a signature of heterogeneous incorporation of N2 in tholins.
authors.affiliation: Synchrotron SOLEIL, DESIRS Beamline , L'Orme des Merisiers, St Aubin, 91192 Gif-sur-Yvette Cedex, France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cunha de Miranda
authors.affiliation: Synchrotron SOLEIL, DESIRS Beamline , L'Orme des Merisiers, St Aubin, 91192 Gif-sur-Yvette Cedex, France.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Garcia
authors.affiliation: Synchrotron SOLEIL, DESIRS Beamline , L'Orme des Merisiers, St Aubin, 91192 Gif-sur-Yvette Cedex, France.|Gas and Aerosol Metrology Department, Chemistry and Biology Division, Laboratoire National de Métrologie et d'Essais - LNE (National Metrology Institute and Testing Laboratory) , 1 rue Gaston Boissier, 75724 Paris Cedex 15, France.
authors.forename: François
authors.initials: F
authors.lastname: Gaie-Levrel
authors.affiliation: Université Versailles St-Quentin; Sorbonne Universités, UPMC Université Paris 06, CNRS/INSU, LATMOS-IPSL , 11 Boulevard d'Alembert, 78280 Guyancourt, France.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Mahjoub
authors.affiliation: Université Versailles St-Quentin; Sorbonne Universités, UPMC Université Paris 06, CNRS/INSU, LATMOS-IPSL , 11 Boulevard d'Alembert, 78280 Guyancourt, France.|NASA Postdoctoral Program, GSFC , Greenbelt, Maryland 20771, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gautier
authors.affiliation: Université Versailles St-Quentin; Sorbonne Universités, UPMC Université Paris 06, CNRS/INSU, LATMOS-IPSL , 11 Boulevard d'Alembert, 78280 Guyancourt, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Fleury
authors.affiliation: Synchrotron SOLEIL, DESIRS Beamline , L'Orme des Merisiers, St Aubin, 91192 Gif-sur-Yvette Cedex, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Nahon
authors.affiliation: Laboratoire de Chimie Physique, UMR8000 CNRS/Université Paris-Sud , 91405 Orsay Cedex, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Pernot
authors.affiliation: Université Versailles St-Quentin; Sorbonne Universités, UPMC Université Paris 06, CNRS/INSU, LATMOS-IPSL , 11 Boulevard d'Alembert, 78280 Guyancourt, France.|Institut Universitaire de France , 103 Boulevard St-Michel, 75005 Paris, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Carrasco