Density effect on excess electron mobility in dense fluids

Abstract

From experimental data, the excess electron mobility in dense simple fluids (rare gases, hydrocarbons) is highly sensitive to the density N and the temperature T of the medium and to the electric field strenght F. Increasing density from dilute gas, the classical dependence μ=C F N disappears around N=0.1 N critical as the binary cross section model fails (Mott's localisation). Then the mobility exhibits a minimum in the critical region and a maximum near N=2 N critical. These features suggest that the motion of the excess electron reflects the dynamics of the atoms in the fluid. We propose a localisation concept and a collisional model relating the electronic motion with the atomic one. All experimental features are well described by our model. Reciprocally, the excess electron transport appears to be a powerful tool to study the intimate structure of the dense dielectric fluids.