The microscopic diffusional and vibrational motions of Na atoms on a (001) Cu surface were studied by means of high-resolution He-atom scattering. The data were analyzed in terms of a Langevin dynamics simulation for adatoms. The observed values for the temperature and parallel wave-vector dependence of the width of the quasi-elastic peak were well-described by the theory, upon making appropriate choices of the potential energy surface and the frictional coupling. The theoretical predictions of the position and width of the lateral frustrated translational mode, made using the same potential and friction, were in excellent agreement with experimental data. The simulation provided a complete determination of the adatom dynamics; including the value of the diffusion constant.

Experimental and Theoretical Investigation of the Microscopic Vibrational and Diffusional Dynamics of Sodium Atoms on a Cu (001) Surface A.P.Graham, F.Hofmann, J.P.Toennies, L.Y.Chen, S.C.Ying: Physical Review B, 1997, 56[16], 10567-78