The atmosphere of Titan, the largest moon of Saturn, is believed to be in some way reminiscent of the primordial atmosphere of Earth, being composed mainly by dinitrogen, methane, simple nitriles like HCN and HCCCN, simple hydrocarbons like C2H6, C2H4 and C2H2, H2 and Ar. Dinitrogen is the prevalent species, being the 97% of the atmosphere and the second relevant constituent is CH4 which represents an average amount of 2.7%. All the other species are present only in trace amounts, but their reactivity is very important as suggested by the plethora of information provided by the NASA/ESA/ASI Cassini-Huygens mission. Atomic nitrogen in its 4S ground state exhibits very low reactivity with closed shell molecules. On the contrary, atomic nitrogen in its first electronically excited 2D state shows a significant reactivity with several molecules identified in the atmosphere of Titan. We have already investigated the reactions of atomic nitrogen in its excited 2D state with various hydrocarbons, like CH4, C2H2, C2H4, C2H6, in laboratory experiments by the crossed molecular beam technique with mass spectrometric detection and time-of-flight analysis at different collision energies complemented by ab initio and kinetics calculations. More recently, with the same approach, we have investigated the reaction between N(2D) and benzene or toluene. In this contribution, we report on a theoretical characterization of the reaction involving N(2D) and benzene or toluene. The aim is to determine the chemical behavior of N(2D) with aromatic species after the previous investigation with aliphatic molecules. In particular, we wish to establish whether the aromatic ring is preserved in this reaction and whether the N atom is incorporated in the ring of carbon atoms. With this aim, we have performed electronic structure calculations of the stationary points along the minimum energy path. These calculations will complement crossed molecular beam experiments which are currently under way and will also be completed by kinetics calculations.

Computational study of the reaction of N(2D) with benzene and toluene: Implications for the upper atmosphere of Titan

ACS Fall 2020 Virtual Meeting

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