Determination of the Na/Cu(001) Potential Energy Surface from Helium Scattering Studies of the Surface Dynamics

Abstract

The quasielastic peak broadening and the frustrated translational vibrations of a low coverage $({\ensuremath{\Theta}}_{\mathrm{Na}}<5%)$ of Na atoms on a Cu(001) surface have been probed with high resolution helium atom scattering. The observed behavior at temperatures between ${T}_{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}150$ and 390 K and for a wide range of parallel wave vectors along the surface symmetry directions is analyzed with a theoretical model based upon Langevin dynamics. Comparison between theory and experiment allows a complete determination of the lateral adsorption potential as well as the frictional coupling of the Na atoms to the substrate.