Reference interaction site model polaron theory of electron mobility in fluids

The reference interaction site model (RISM)-polaron model of excess electrons in liquids is extended to treat the competition between attractive and repulsive branches of electron-liquid atom pseudopotentials. For certain choices of parameters, a delicate cancellation occurs leading to unusually large values of electron mobility over a narrow range of liquid densities. This behavior has also been observed in experiment. The RISM-polaron theory is used to interpret these experiments. It is shown that because of the topological disorder of a liquid, attractive interactions alone lead to electron localization and no anomalously large mobilities. Similarly, repulsions by themselves do not produce the anomaly. The cancellation that can occur is a manifestation of the quantum nature of electronic states in an annealed random system. Comparison of the present results with those that might follow from a classical percolation model suggests that the latter does not provide a correct description of electron mobilities in liquids. The cancellation is different but analogous to the Ramsauer–Townsend effect.