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On the gas-phase formation of the HCO− anion: Ac- curate quantum study of the H−+CO radiative associ- ation and HCO radiative electron attachment

Abstract

The hydrogen anion has never been observed in the interstellar medium, but it is most likely present in some interstellar regions. Since a direct detection appears especially difficult, im- proving the knowledge of the astrochemical processes involving this anion should be valuable in defining a way of indirect detection. We present the first study of the radiative association of H− and CO to form the HCO− anion within a quantum time-independent approach. We use a state-of-the-art potential energy surface which has been calculated for the present study. The calculated radiative association rate coefficient is monotonically decreasing from 6 × 10−16 to 5 × 10−19 cm3 molecule−1 s−1 across the 0.01–1000 K temperature range. At the typical temper- ature of the cold interstellar medium, namely ∼10 K, the radiative association rate is ∼2 × 10−17 cm3 molecule−1 s−1. On the other side the plane wave approximation is used to calculate the HCO radiative electron attachment rate coefficient. It is found to be almost constant and also equal to 2× 10−17 cm3 molecule−1 s−1. Setting aside the question of the abundances of the reactants of both processes, these results demonstrate that among the two gas-phase modes of production of the HCO− anion in cold interstellar medium considered in this study, the H−+CO ra- diative association is dominating below 10 K while the radiative electron attachment rate is larger above 10 K.

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Publication details

The article was received on 28 May 2018, accepted on 27 Jun 2018 and first published on 28 Jun 2018


Article type: Paper
DOI: 10.1039/C8FD00103K
Citation: Faraday Discuss., 2018, Accepted Manuscript
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    On the gas-phase formation of the HCO− anion: Ac- curate quantum study of the H−+CO radiative associ- ation and HCO radiative electron attachment

    T. Stoecklin, P. Halvick, M. D. J. Lara-Moreno, T. Trabelsi and M. Hochlaf, Faraday Discuss., 2018, Accepted Manuscript , DOI: 10.1039/C8FD00103K

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