| Abstract
| - We present results of classical trajectory (CT) calculations on the sticking of protons to the basalplane (0001) face of crystalline ice, for normal incidence at a surface temperature (Ts) of 80 K. Thecalculations were performed for moderately low incidence energies (Ei) ranging from 0.05 to 4.0 eV.Surprisingly, significant reflection is predicted at low values of Ei (≤ 0.2 eV) due to repulsive electrostaticinteractions between the incident proton and the surface water molecules with one of their H-atoms pointingupward toward the gas phase. The sticking probability increases with Ei and converges to unity for Ei ≥0.8 eV. In the case of sticking, the proton is trapped in the ice forming a Zundel complex (H5O2+), with anaverage binding energy of 9.9 eV with a standard deviation of 0.5 eV, independent of the value of Ei. Innearly all sticking trajectories, the proton is implanted into the ice surface, with a penetration depth thatincreases with Ei. The strong interaction with the neighboring water molecules leads to a local rupture ofthe hydrogen bonding network, resulting in collision induced desorption of water (puffing), a process thatoccurs with significant probability even at the lowest Ei considered. The probability of water desorptionincreases with Ei. In nearly all trajectories in which water desorption occurs, a single three-coordinatedwater molecule is desorbed from the topmost monolayer.
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