ON THE MARCUS MODEL OF ELECTRON-TRANSFER AT IMMISCIBLE LIQUID INTERFACES AND ITS APPLICATION TO THE SEMICONDUCTOR LIQUID INTERFACE

We report calculations for electron transfer rates at immiscible liqui d interfaces with new models closely related to a model originally dev eloped by R.A. Marcus. We compare our modified models both with the or iginal Marcus model and with an adaptation of it by N.S. Lewis to elec tron transfer at the semiconductor-liquid interface. On the basis of t hese comparisons and a thorough examination of the foundations of both the Marcus and Lewis models, we find no basis for the assertion in th e literature that the Lewis model can be used to calculate an upper li mit for the electron transfer rate constant at the semiconductor-liqui d interface. Features we discuss of the Lewis model and a related mode l by H. Gerischer show that these semiconductor-liquid interface ET mo dels are evidently not physically plausible. We also conclude that whi le the Marcus model appears to be a physically plausible first order m odel for immiscible liquid systems, in its present form it does not se em that it can produce reliable quantitative estimates for real liquid -liquid systems. Our enhancements, both suggested and implemented here , of the Marcus model appear to offer the potential for constructing a ugmented and better defined models for immiscible liquid ET.