Model of thermalization of quasifree electrons in high-mobility liquids and its relationship with electron mobility

Abstract

The present paper aims at constructing a theoretical model in terms of which the relationship between the free‐ion yield and electron mobility may be understood for high‐mobility liquids. The framework chosen for that purpose is the Fokker–Planck equation with the Coulomb field of the electron and the sibling cation built into it. This equation describes, in general, the distribution function for the electrons in both the configurational and velocity spaces. Starting from a given initial position and velocity, one can calculate the distribution of thermalization distances through the use of a relaxation time. The same relaxation time appears in the mobility equation, implying the similarity of energy‐loss processes of low‐energy electrons following an ionization event and of electrons slightly heated up by the external field. The model therefore provides, in principle, a connection between the electron mobility and the free‐ion yield. In practice the agreement between theory and experiment is reasonably good for molecular hydrocarbons but is poor for liquefied rare gases.