The diffusive motion of O atoms, which were adsorbed on (00▪1) Ru surfaces, was observed at the atomic scale by means of scanning tunnelling microscopy with a temporal resolution of about 10ms at room temperature. The mean residence times of O atoms, in the neighborhood of other O atoms, were extracted from a statistical analysis of changes in atomic configurations over sequences of more than 1000 images. The residence times varied by more than an order of magnitude over distances of 3 lattice constants. This indicated the need to include lateral interactions when modelling collective phenomena such as surface diffusion or reactions.

Dynamics of Adatom Motion under the Influence of Mutual Interactions: O/Ru(0001). S.Renisch, R.Schuster, J.Wintterlin, G.Ertl: Physical Review Letters, 1999, 82[19], 3839-42