The irradiation of water ice by C$^+$ ions in the cosmic environment
  We present a first principles molecular dynamics (FPMD) study of the
interaction of low energy, positively charged, carbon (C+) projectiles with
amorphous solid water clusters at 30 K. Reactions involving the carbon ion at
an initial energy of 11 eV and 1.7 eV with 30-molecule clusters have been
investigated. Simulations indicate that the neutral isoformyl radical, COH, and
carbon monoxide, CO, are the dominant products of these reactions. All these
reactions are accompanied by the transfer of a proton from the reacting water
molecule to the ice, where it forms a hydronium ion. We find that COH is formed
either via a direct, "knock-out", mechanism following the impact of the C+
projectile upon a water molecule or by creation of a COH_2^+ intermediate. The
direct mechanism is more prominent at higher energies. CO is generally produced
following the dissociation of COH. More frequent production of the formyl
radical, HCO, is observed here than in gas phase calculations. A less commonly
occurring product is the dihydroxymethyl, CH(OH)_2, radical. Although a minor
result, its existence gives an indication of the increasing chemical complexity
which is possible in such heterogeneous environments.
