Kinetics and Branching for the Reactions of N2+ with C3H4 Isomers at Low Temperatures and Implications for Titan’s Atmosphere
| Autor: | Ahmad Mortada, Sophie Carles, Sándor Demes, Baptiste Joalland, François Lique, Abdessamad Benidar, Panayotis Lavvas, Ludovic Biennier |
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| Přispěvatelé: | Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), ANR-14-CE33-0013, Agence Nationale de la Recherche, Centre National de la Recherche Scientifique, Commissariat ? l'énergie Atomique et aux énergies Alternatives, Centre National d'Etudes Spatiales, ANR-14-CE33-0013,Anion Cos Chem,Explorer la Chimie et Spectroscopie des Anions Cosmiques(2014) |
| Rok vydání: | 2022 |
| Předmět: |
[PHYS]Physics [physics]
[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry temperature-dependent reactivity reactive collisions Atmospheric Science uniform supersonic flows astrochemistry [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] Space and Planetary Science Geochemistry and Petrology planetary sciences [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] Molecular physics |
| Zdroj: | ACS Earth and Space Chemistry ACS Earth and Space Chemistry, 2022, 6 (5), pp.1227-1238. ⟨10.1021/acsearthspacechem.1c00347⟩ |
| ISSN: | 2472-3452 |
| DOI: | 10.1021/acsearthspacechem.1c00347 |
| Popis: | International audience; The photoionization of N2 plays a key role in initiating the formation of complex organic molecules in the nitrogen-rich atmosphere of Saturn’s largest moon, Titan. To date, only a handful of laboratory studies have explored the reactivity of N2+ ions with hydrocarbons─limited to methane, acetylene, and ethylene─at the low temperatures relevant to Titan. Here, the rate coefficients, product identity, and branching ratios of the ion–molecule reactions of N2+ with C3H4 isomers, namely, propyne CH3CCH and allene CH2CCH2, were measured between 24 and 72 K in uniform supersonic flows. The rate coefficients are collisional and their temperature dependence is in remarkable agreement with capture models. The outcomes of both reactions are similar: they proceed primarily via dissociative charge transfer, leading to the formation of C3H3+ (main product, >70%) and C3H2+ (between 9 and 17%), whereas a second, nondissociative charge-transfer mechanism leading to C3H4+ becomes slightly more prominent as the temperature decreases (from 3 to 12%). C3H3+ is plausibly formed predominantly as the smallest aromatic cation, cyclopropenyl c-C3H3+, by following the lowest-energy pathway for the decomposition of allene and propyne cations. The measured rate coefficients and branching ratios were included in a photochemical model of Titan’s atmosphere. The results point toward a secondary role of N2+ + C3H4 reactive pathways in the production of c-C3H3+. |
| Databáze: | OpenAIRE |
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