ON THE KINETICS OF DIFFUSIVE LIQUID LIQUID INTERFACIAL TRANSPORT - MEAN-PASSAGE-TIME SOLUTION AND THE CHEMICAL PICTURE

The chemical picture for the transport of matter across a liquid-liquid interface assumes that the overall process can be adequately described by a single rate constant. The present work is aimed at systematic examination of this principle for particles moving on a model potential surface of a particular shape, which contains either a barrier or a well and which obeys a Smolu-chowski equation. A semi-analytic solution is found, and the result is compared with both the mean-passage-time result obtained in the present paper and with other available theories of diffusive processes. These theories, which are practically equivalent for high potential barriers, prove to differ significantly when the barrier height is less than 3kBT. Considering the case of a potential well leads to the conclusion that the transient regime, during which the time evolution of the transfer is not accurately described by the leading exponential of the eigenfunction expansion, is much longer than for a potential barrier. While the common theories of diffusive processes are not applicable to a potential well, the mean-passage-time result still gives the correct time scale for the phenomenon. © 1990 Taylor & Francis Ltd.