Diffusion measurements on interactive systems

The nonlinearity of the diffusion process in interactive systems suggests a classification of the methods that measure diffusion coefficients into equilibrium and nonequilibrium ones. Diffusion coefficients obtained by different methods, in general, do not agree with each other. This is shown explicitly with the use of Monte Carlo simulations by comparing results obtained with an equilibrium method (fluctuation method) and a nonequilibrium one (laser-induced-desorption method). However, the same microscopic information about the interactions between the particles can be obtained by any method with proper modeling.