Xe monolayer adsorption on Ag(111) I. Structural properties

The monolayer of adsorbed xenon on the ( ?1) surface of silver was studied using low- energy electron diffraction. The structure is an hexagonal lattice aligned with but out of registry with the substrate. The Xe-Xe spacing at 25 K is 4.44 ± 0.01 Å in the full monolayer and 4.47 ± at less than full coverage. The Xe-Ag spacing is 3.5 ± 0.1 Å. Here {<u _⊥> ²}/{T}, the meansquare vibrational amplitude normal to the surface divided by the temperature is (1.83 ± 0.4 × 10 ^-4 A ²/K. The heat of adsorption is 0.28 ± 0.03 eV/atom.