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Is the Gas-phase OH+H2CO Reaction a Source of HCO in Interstellar Cold Dark Clouds? A Kinetic, Dynamic, and Modeling Study

Abstract : Chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T∼10-100K). Scarce kinetic information is currently available for this kind of reactions at T<200 K. In this work we use the CRESU (, which means Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients () of the gas-phase OH+HCO reaction between 22 and 107 K. values greatly increase from 2.1×10 cm s at 107 K to 1.2×10 cm s at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and potential energy surface, recently developed which generates highly accurate potential and includes long range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+HCO reaction. In order to revisit the chemistry of HCO in cold dense clouds, is reasonably extrapolated from the experimental results at 10K (2.6×10 cm s). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 10-10 yrs. The different sources of production of HCO are presented and the uncertainties in the chemical networks discussed. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. The present reaction is shown to account for a few percent of the total HCO production rate. Extensions to photodissociation regions and diffuse clouds environments are also commented.
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Contributor : Laurent Jonchère <>
Submitted on : Thursday, January 11, 2018 - 1:49:17 PM
Last modification on : Wednesday, March 31, 2021 - 2:11:34 PM

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A. J. Ocana, E. Jimenez, B. Ballesteros, André Canosa, M. Antiñolo, et al.. Is the Gas-phase OH+H2CO Reaction a Source of HCO in Interstellar Cold Dark Clouds? A Kinetic, Dynamic, and Modeling Study. The Astrophysical Journal, American Astronomical Society, 2017, 850 (1), pp.28. ⟨10.3847/1538-4357/aa93d9⟩. ⟨hal-01681152⟩



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