Electron transport in dense gases: limitations on the Ioffe-Regel and Mott criteria

Abstract

In the gas phase, the Ioffe–Regel criterion that electron transport becomes modified when the mean free path equals the electron wavelength (L = λ) applies clearly only to helium and hydrogen, which have a net repulsive interaction with electrons. The Mott criterion, that when L = λ/2π the electron is in a localized state, also applies to these two gases. The two criteria are less effective for molecules that have net attractive interactions with the electrons, because the interactions are not simply additive. They are not useful for xenon gas. The criteria are also assessed for: (a) several highly polarizable, spherical and nonspherical molecules; (b) polar molecules; (c) nitrogen and carbon dioxide, which form transient anions.