ISSN:
1089-7690
Quelle:
AIP Digital Archive
Thema:
Physik
,
Chemie und Pharmazie
Notizen:
We present calculations on the sticking of hyperthermal HCl to the basal plane (0001) face of ice Ih at normal and off-normal incidence. The dependence of the sticking probability on the incidence energy (Ei), the angle of incidence (θi), and the surface temperature (Ts) is discussed. Two sticking mechanisms are observed. For θi≤30°, penetration of the (0001) face is possible at an energy of about 100 kJ/mol, which is an order of magnitude lower than energies for which the penetration of metallic or covalently bonded crystals by atoms becomes possible. This possibility is due to the open structure of single-crystalline ice Ih, in which the water molecules are arranged in superimposed hexagons, forming shafts running perpendicular to the ice surface. The penetration mechanism is operative for the entire range of Ts studied (110–190 K). The second sticking mechanism, i.e., adsorption, occurs for all Ei, θi, and Ti. For θi〈45°, the adsorption probability increases with θi as would be expected, because the normal component of Ei that needs to be transferred to the surface for sticking to occur scales with cos2 θi. However, for θi≥45°, the adsorption probability decreases with θi. The energy transfer from HCl to the ice surface and the energy dissipation within the surface are found to be fast and efficient at normal incidence. © 2001 American Institute of Physics.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.1377885
Permalink