THEORY OF TRACER EXCHANGE IN SINGLE-FILE SYSTEMS

Tracer exchange in single-file systems (one-dimensional diffusional sy stems where the particles are not able to pass each other) shows pecul iar and interesting features which differ considerably from that of tr ansport diffusion or from the behaviour known from ordinary diffusiona l systems. A formalism relating the tracer exchange curve (as the obse rvable of the tracer exchange experiment) to the residence time distri bution (describing the intracrystalline diffusional mechanism) and the boundary condition (describing the situation outside) is introduced. The formalism is guite general and valid for any diffusional regime. T ypical examples of the residence time distribution of a single-file sy stem can be inferred from the tracer exchange curves obtained in a pre vious study by numerical simulations. Based on these examples, the tra cer exchange curves for the single-file system subject to different bo undary conditions (corresponding to a variety of experimental set-ups) are plotted and discussed.