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Communication Dans Un Congrès Année : 2019

Kinetics of the reaction between the CN radical and methanol at low temperatures using the CRESU technique

Ilsa R. Cooke
Divita Gupta
Théo Guillaume
Thomas Hearne
Brian M. Hays
Ian R Sims

Résumé

The interstellar medium is host to a rich chemistry that produces a number of complex organic molecules (COMs) i.e. organic molecules with six or more atoms. A large number of COMs have been observed in astrophysical regions, even in very cold (<10 K) environments, challenging the widely accepted "warm-up" model in which COMs are formed on the surface of icy dust grains and delivered to the gas phase during star-formation. Methanol (CH3OH) is a COM of particular interest because it is an important parent species of larger and more complex molecules in the gas and ice phases. Neutral-radical reactions are an important destruction route for many species and, given the widespread abundance of the CN radical in space, the reaction between methanol and the CN radical is of significant interest. Here, we study the kinetics of the reaction between CH3OH and the CN radical using the well-established CRESU (Reaction Kinetics in Uniform Supersonic Flow) technique, combined with Pulsed Laser Photolysis-Laser-Induced Fluorescence (PLP-LIF). Our results display a negative temperature dependence, typical of what has been seen previously for other radical-neutral reactions that do not possess potential barriers. The rate coefficient obtained at room temperature strongly disagrees with that measured by Sayah et. al. in a flow cell. The reaction products and their branching ratios are of significant interest, particularly the branching ratio between the radicals methoxy (CH3O) and hydroxy-methanol (CH2OH). While the PLP-LIF technique is a powerful technique for the measurement of overall, temperature-dependent reaction rate coefficients, it is not well suited to measurements of product branching ratios. We are conducting electronic structure calculations for this reaction in order to provide a theoretical perspective. We are also developing a new setup integrating chirped-pulse broad-wave microwave spectroscopy with continuous flow-CRESU (CRESUCHIRP), which will allow us to identify reaction products and their branching ratios.
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Dates et versions

hal-02282223 , version 1 (11-09-2019)

Identifiants

  • HAL Id : hal-02282223 , version 1

Citer

Ilsa R. Cooke, Divita Gupta, Sidaty Cheikh Sid Ely, Théo Guillaume, Thomas Hearne, et al.. Kinetics of the reaction between the CN radical and methanol at low temperatures using the CRESU technique. 38EME EDITION DU COLLOQUE ANNUEL DU GROUPE FRANÇAIS DE CINETIQUE ET PHOTOCHIMIE (GFCP), Jun 2019, Rennes, France. ⟨hal-02282223⟩
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