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Ion-Ice Astrochemistry: Barrierless Low-Energy Deposition Pathways to HCOOH, CH3OH, and CO2 on Icy Grain Mantles from Precursor CationsA new family of very favorable reaction pathways is explored involving the deposition of ions on icy grain mantles with very low energies. Quantum chemical cluster calculations at the MP2/6-31+G** level in 4H2O clusters and at the B3LYP/6-31+G** level in 17H2O clusters indicate that HCO+ and CH3 + are able to react spontaneously with one of the water molecules in the cluster to form protonated formic acid (HCOOH2 +) and protonated methanol (CH3OH2 +), respectively. It is furthermore found that these initial adducts spontaneously transfer their excess protons to the cluster to form neutral formic acid and methanol, plus solvated hydronium, H3O+. In the final case, if a CO molecule is bound to the surface of the cluster, OH+ may react with it to form protonated carbon dioxide (HCO2 +), which then loses its proton to yield CO2 and H3O+. In the present model, all of these processes were found to occur with no barriers. Discussion includes the analogous gas phase processes, which have been considered in previous studies, as well as the competitive abstraction pathway for HCO(+) + H2O.
Document ID
20110023633
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Woon, David E.
(Illinois Univ. at Urbana-Champaign Urbana, IL, United States)
Date Acquired
August 25, 2013
Publication Date
January 18, 2011
Publication Information
Publication: The Astrophysical Journal
Volume: 728
Issue: 1
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NNX07AN33G
Distribution Limits
Public
Copyright
Other

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