Experimental and theoretical investigation of the microscopic vibrational and diffusional dynamics of sodium atoms on a Cu(001) surface

The microscopic diffusional and vibrational motion of sodium atoms on a Cu(001) surface have been;studied with high-resolution helium atom scattering. The data are analyzed through a Langevin dynamics simulation for the adatoms. The observed values for the temperature and parallel wave-vector dependence of the width of the quasielastic peak are well described by the theory with an appropriate choice of potential energy surface and the frictional coupling. The theoretical prediction for the position and width of the lateral frustrated translational mode using the same potential and friction are in excellent agreement with the corresponding experimental data. The simulation thus provides a complete determination of the adatom dynamics including the value of the diffusion constant. [S0163-1829(97)01840-7] .