Experiments were considered in which the trajectories of individual molecules or atoms at surfaces were observed by means of scanning microscopy. A scanning probe moves along the surface and excited the molecule so that the molecule's location was deduced from the times at which fluorescence photons were emitted. Operation of other types of scanning microscopes could be described by similar models. The observed trajectories were inherently affected by the interaction between the molecule and the probe such that the measured diffusion coefficient depended on the frequency at which the surface was scanned. The number of photons emitted by the molecule during a scan was affected in a nontrivial way by its mobility. If photo-excitation increased the mobility, emission was found to be suppressed.

Observation of Single Molecule Transport at Surfaces via Scanning Microscopies: Monte Carlo Wave Function Study of a Model Problem. D.E.Makarov: Physical Review E, 2002, 65[5], 051601