An interplay between experimental measurements of tracer diffusion and its theoretical interpretation was presented which led to good estimates of the interaction of an adparticle with the surface. It was shown how the results of 3 different experimental techniques, field ion microscopy, scanning tunnelling microscopy and quasi-elastic He atom scattering, could be interpreted. By using the generalized Langevin equation as a model for the diffusion dynamics, it was shown how the turnover theory for activated diffusion could be used to describe the measured time evolution of the adparticle distribution on the surface. The differing activation energies measured for hopping over single or double lattice lengths was shown to arise from the added energy loss to the surface as the particle moved over the longer path. Some of the issues which remained unclear included quantum effects, such as the quantum suppression of diffusion, vibrationally assisted diffusion, multi-dimensional effects and diffusion in the presence of external fields.The Dynamics of Activated Surface Diffusion. S.Miret-Artés, E.Pollak: Journal of Physics - Condensed Matter, 2005, 17[49], S4133-50