Quasielastic Helium Atom Scattering from a Two-Dimensional Gas of Xe Atoms on Pt(111)

Quasielastic helium atom scattering provides direct evidence for a fully mobile two-dimensional gas of Xe atoms on Pt(111) at a coverage of ΘXe0ex0ex=0ex0ex0.017 and a temperature of Tₛ0ex0ex=0ex0ex105K. Molecular dynamics simulations of the experimental data show that the frictional coupling rate between the Xe atoms and substrate is less than 0.25ps^-1 and the lateral potential corrugation for single Xe atoms is less than 9.6 meV, which is only $40%$ of the value previously determined at high coverage.