Protons Colliding with Crystalline Ice: Proton Reflection and Collision Induced Water Desorption at Low Incidence Energies
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- 作者：Pepa Cabrera Sanfelix ; Ayman Al-Halabi ; George R. Darling ; Stephen Holloway ; and Geert-Jan Kroes
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：March 23, 2005
- 年：2005
- 卷：127
- 期：11
- 页码：3944 - 3951
- 全文大小：311K
- 年卷期：v.127,no.11(March 23, 2005)
- ISSN：1520-5126
文摘
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.
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.