THEORY AND SIMULATION OF MULTIPLE-TRAPPING TRANSPORT THROUGH A FINITESLAB

The theory of the multiple-trapping model for dispersive transport is formulated for the case of a continuous distribution of trapping level s. The density of particles and the current are expressed in terms of the waiting-time distribution for release. Numerical simulations of th e multiple-trapping model are performed for an exponential distributio n of trapping levels and complete agreement with the theoretical expre ssions is found. The apparent exponents of the power-law behavior of t he current in the drift and extraction regimes are investigated. The e xponent in the extraction regime approaches the scaling prediction onl y asymptotically, at, very long times, except around one particular va lue. Results for the time-dependent energy distribution of the trapped particles are also given.