Theory of electron mobility in dense gases

Abstract

A new extended theory of electron transport in dense gases is presented. It is shown that positive and negative density effects can be explained in terms of a single unifying theory. The agreement between theory and experiment is extremely good over a wide range of pressure and temperature in gases with a negative effect, such as He and H2. Some further improvements of the theory in gases with elevated polarizability seem to be necessary for a better quantitative agreement with experimental data, even if the agreement in Ar makes us confident that the proposed theoretical approach can be correct. In the light of our unifying theory, previous theoretical models are analyzed and it is shown that almost all can be obtained under special conditions.

Excess electron mobility in high-density argon gas

“…All these theories are based on a complex shift of the electron kinetic energy in a dense disordered medium [ll -13]. In their present form [14,15] these theories, however, disagree more or less with experimental data. For instance, for the negative-density effect in He and Ne multiple-scattering theories predict an exponential decrease of poN with the gas density N [14], where v(s) = (2s/rn) I NoM(s) is the collision rate, 27rh2 Vp -= 6= Na (4) is the real part of the total-energy shift as calculated by Fermi [ll], and a is the scattering length of the atom.…”

“…For positive-scattering-length gases we have [15] is the classical prediction for poN, AT = h/ (2xrnksT) I is the electron thermal wavelength, and oM and crT are the momentum transfer and total scattering cross sections, respectively. Equation (1) is obtained for medium to low densities by assuming a nearly constant scattering cross section.…”

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

“…The latter seems clear enough. The former is obscured by the wide variety of treatments of the average electron wavelength (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). The different treatments cause differences up to eleven-fold in the predicted densities where multibody scattering should become important (see Appendix 1).…”

Electron mobility in dense Argon gas at several temperatures

“…However, in contrast to the MS theories, it assumes that only the kinetic part of the shift affects the mobility in the same way for both attractive and repulsive gases, whereas the MS theories introduce different mechanisms of action according to the sign of the total energy shift [17][18][19]25]. …”

“…Several multiple scattering theories have been developed, in the limit of vanishingly small electric fields, to rationalize the experimental observations [17][18][19].…”