Phenomenological Theory of the Mobility of an Electron in Dense Helium Gas

A phenomenological theory is used to account for the observed variation of the mobility of electrons in high-density low-temperature helium gas. Thermodynamic relaxation times are introduced to characterize the lifetime of localized and delocalized states. By allowing these relaxation times to be a function of the helium density, we are able to account quantitatively for the density dependence of the electronic mobility and the anomalous electric field dependence of the electron drift velocity, as observed by Levine and Sanders. The computed critical density, where the free energy of the localized configuration is equal to the free energy of the delocalized state, is 9.5 × ${10}^{20}$ atoms/${\mathrm{cm}}^3$.