AN ELECTROCHEMICAL MODEL OF LOW-FREQUENCY DISPERSION

The widely observed phenomenon of low-frequency dispersion is interpre ted in terms of an electrochemical process in which ionic charge carri ers migrating under the action of an external field combine to form ne utral molecules, thereby eliminating charges which would be necessary to sustain the very high capacitances at low frequencies. Both chargin g and discharging currents are almost independent of time with the dis charge currents consistently lower than the charging currents. The neu tral molecules provide a reservoir of charge and of energy which becom e released on discharging the system after step-function charging, mos t of the charge and energy being dissipated in what is a highly lossy system. The frequency-domain response is then interpreted using the ne w concept of ''energy criterion'' which is particularly suited to the analysis of fractional power-law dependence on frequency. This provide s a self-consistent and realistic theory of low-frequency dispersion a nd enables the connection to be made between time and frequency-domain responses, despite the fact that the strong non-linearity of the resp onse makes the Fourier transformation of limited usefulness.