Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 458, Issue 3, Pages 2953-2961Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stw373
Keywords
astrochemistry; molecular data; molecular processes; methods: laboratory; ISM: molecules
Categories
Funding
- French National PCMI programme - CNRS
- DIM ACAV
- Region Ile de France
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The amount of methanol in the gas phase and the CO depletion from the gas phase are still open problems in astrophysics. In this work, we investigate solid-state hydrogenation of CO-bearing species via H-exposure of carbon monoxide, formaldehyde, and methanol-thin films deposited on cold surfaces, paying attention to the possibility of a return to the gas phase. The products are probed via infrared spectroscopy (reflection absorption infrared spectroscopy), and two types of mass spectroscopy protocols: temperature-programmed desorption, and during-exposure desorption techniques. In the case of the [CO+H] reactive system, we have found that chemical desorption of CO is more efficient than H-addition reactions and HCO and H2CO formation; the studies of the [H2CO + H] reactive system show a strong competition between all surface processes, chemical desorption of H2CO, H-addition (CH3OH formation) and H-abstraction (CO formation); finally, [CH3OH + H] seems to be a non-reactive system and chemical desorption of methanol is not efficient. CO-bearing species present a see-saw mechanism between CO and H2CO balanced by the competition of H-addition and H-2-abstraction that enhances the CO chemical desorption. The chemical network leading to methanol has to be reconsidered. The methanol formation on the surface of interstellar dust grain is still possible through CO+ H reaction; nevertheless, its consumption of adsorbed H atoms should be higher than previously expected.
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