Gas-phase reactivity of CH₃OH toward OH at interstellar temperatures (11.7–177.5 K): experimental and theoretical study

Abstract

New kinetic data and product distributions have been obtained using the experimental CRESU technique combined with a theoretical analysis of the reaction mechanism. The astrophysical implications of fast CH3O and CH2OH formation are discussed.

Quantum Roaming in the Complex-Forming Mechanism of the Reactions of OH with Formaldehyde and Methanol at Low Temperature and Zero Pressure: A Ring Polymer Molecular Dynamics Approach

“…This branching ratio can be directly obtained from Ref. 23 The agreement obtained with the experimental data for the CH 3 OH + OH reaction is really good, but further theoretical analysis should be done to completely confirm the results. In particular, the calculation of the k tunnel /[k tunnel + k rediss ] ratio as a function of temperature has to be recalculated including more dimensions.…”

Gas-phase reactivity of CH3OH+OH down to 11.7 K: Astrophysical implications

“…It has been confirmed that k (T ) abruptly increases by almost 2 orders of magnitude from 177.5 K to around 100 K. At T <100 K, this increase is less pronounced, reaching the capture limit at temperatures below 22 K (Figure 1. ) (Ocaña et al (2019)).…”

Gas phase reaction kinetics of complex organic molecules at temperatures of the interstellar medium: The OH + CH3OH case

“…In 2019, the Ciudad Real group did an extensive experimental work in which they evaluated the pressure dependence of the reaction for several temperatures ranging in between 12 and 180 K (Ocaña et al 2019). No pressure dependence was observed below 100 K whereas comparison with the Leeds work suggested some pressure dependence in the range 120 -150 K. Experiments were completed by theoretical calculations using the Multi-Conformer Canonical TST and RRKM methods for determining the HPL and LPL regimes respectively.…”

“…The authors were able to match the experimental results assuming a pressure between 200 and 3000 Torr which is however many orders of magnitude higher than the experimental conditions (∼0.1 -1 Torr). Similarly to the work by (Ocaña et al 2019), energy barriers were also adjusted with respect to the ab initio results. Interestingly, Nguyen et al showed that the rate constant was pressure independent for P 2 Torr and T 100 K. This indicates that the LPL regime is still valid at significant pressures embedding the experimental conditions.…”

“…All these results have been obtained using CRESU reactors (French acronym for Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flows), a well-established technique for the study of gas-phase reaction kinetics at very low temperatures (Potapov et al 2017). From a theoretical point of view the interest for reactions involving COMs has considerably grown recently and several reactions mentioned in Table 1 have been investigated at interstellar temperatures with a special attention paid on OH + CH 3 OH (Shannon et al 2013;Gao et al 2018;Roncero et al 2018;Ocaña et al 2019;Nguyen et al 2019;del Mazo-Sevillano et al 2019) because of its potential importance in the formation of CH 3 O (see next section). In the present paper we will review the recent experimental and theoretical works carried out concerning this reaction and will comment about its significance for the chemistry of molecular clouds.…”