An experimental investigation of the nuclear spin relaxation of single alkali-metal atoms, adsorbed at hot (1000 to 1300K) metal surfaces, permitted a study to be made of adatom diffusion. In particular, the magnetic field dependence of the relaxation rate probed the characteristic spectral density of the diffusion process. The theoretical background was developed and was applied to published data for 7Li which was adsorbed at O-covered W(110). The magnetic field dependence, as well as the temperature dependence, were well-described by a spectral density which exhibited a logarithmic divergence in the low-frequency (high-temperature) limit. It was determined by the correlation function for 2-dimensional diffusion. Analysis of the data permitted the determination of the activation energy and the pre-exponential factor for diffusion in the limit of very small coverages (less than 0.001).

M.Riehl-Chudoba, U.Memmert, D.Fick: Surface Science, 1991, 245[1-2], 180-90