The atmosphere of Titan is mainly composed of molecular nitrogen, with a few percent of methane and small amounts of hydrocarbons as well as traces of nitrogen and oxygen-bearing species. Nitrogen atoms in the excited metastable 2D state can be produced in the upper atmosphere by several processes involving N2 (photodissociation, electron dissociation, etc.). Since deactivation of N(2D) by N2 is a slow process, the main fate of N(2D) above 800 km is chemical reaction with other constituents of Titan's atmosphere. In order to assess the role of N(2D) reactions and improve our understanding of the neutral chemistry that controls the formation of N-containing organic compounds in the atmosphere of Titan, as well as that of other bodies where both N2 and hydrocarbons are present, such as Uranus and Neptune, there is the need of measuring reaction rate constants at the relevant temperatures - and this can be best done using the CRESU kinetics technique - but also to know the primary reaction products as well as their branching ratios (BRs), because this can strongly affect the accuracy of photochemical models. Primary products and BRs can be best obtained from crossed molecular beam (CMB) experiments with mass-spectrometric detection, empowered with soft ionization detection. Interpretation of CMB results is often assisted by ab initio calculations of the underlying potential energy surfaces and RRKM statistical estimates, and possibly also dynamics computations, of BRs. In this talk we will focus on our recent CMB and theoretical studies of reactions relevant to the atmosphere of Titan, such as those of N(2D) with methane, ethane, acetylene, ethylene, hydrogen and water. Results on reactions of CN radicals with unsaturated hydrocarbons will also be discussed briefly. Acknowledgements. This research is supported by MIUR (PRIN 2010-2011) and EC COST action CM0805 �The Chemical Cosmos�.

Molecular beam and theoretical studies on the reaction dynamics of N(<sup>2</sup>D) and CN radicals relevant to the atmospheric chemistry of Titan

246th National Meeting (2013)

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Molecular beam and theoretical studies on the reaction dynamics of N(2D) and CN radicals relevant to the atmospheric chemistry of Titan

Molecular beam and theoretical studies on the reaction dynamics of N(²D) and CN radicals relevant to the atmospheric chemistry of Titan