Theory of Low-Energy Electron Scattering by Polar Molecules

Abstract

The total diffusion cross section is calculated for low-energy impact of electrons upon polar molecules in an approximation which treats the molecules as fixed rotators. The amplitude is evaluated and the differential cross section corresponding to fixed orientation of the molecule is then averaged over the Maxwell distribution. It is shown how this simple approach follows from an adiabatic approximation to the excitation amplitudes. The results show excellent agreement with available data.

Analytic solution of the wave equation for an electron in the field of a molecule with an electric dipole moment

“…In the latter, this interest was fueled by the observation that electron capture by a frozen molecule with a permanent electric dipole moment could take place only if the dipole moment exceeds a certain minimum critical value [2]. Another source of interest came from early experimental work on the scattering of low energy electrons by such molecules, which exhibited peculiar features [3]. Moreover, the electron binding properties of polar molecules have been the topic of considerable theoretical and experimental interest [4].…”

Interaction Of Thermal Electrons With Polar Molecules

“…Cross sections for momentum transfer from electron to polar molecule deduced from these experiments and the literature are compared with the "point dipole" theories of Altshuler (1957) and Mittleman and Von Holdt (1965).…”

“…An exact theory that relates the cross section for momentum transfer (electron to molecule) to the dipole moment f-Iof a "point" dipole has now been published by Mittleman and Von Holdt (1965). As f-I-increases, the exact theory deviates strongly from the first Born approximation calculation of Altshuler (1957) (see Fig. 3), which has been used in previous comparisons of experiment with theory (Pack, Voshall, and Phelps 1962;Hurst, Stockdale, and O'Kelly 1963;Christophorou, Hadjiantoniou, and Hurst 1965).…”

“…In calculating momentum transfer cross-section ratios, average values of SW 2 were used for the range 0·01 <;; EIP <;; 0·1 V cm-1torr-I, for which the electron swarm contains a thermal (Maxwellian) distribution of electron velocities (Stockdale and Hurst 1964). Knowledge of the velocity distribution makes possible theoretical estimates of AI/A2 from the theories of Altshuler (1957) or Mittleman and Von Holdt (1965). Figure 3 summarizes the experimental data, from the present work and from the literature, on momentum transfer cross sections for electrons to polar molecules.…”

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SummaryDrift velocities of thermal electron swarms have been measured in pure ethylene gas and in mixtures of acetone, ethanolamine, ethylene diamine, ethanol, n-propanol, isopropanol, chlorobenzene, diethyl ether, diethylamine, and propane with ethylene.Cross sections for momentum transfer from electron to polar molecule deduced from these experiments and the literature are compared with the "point dipole" theories of Altshuler (1957) and Mittleman and Von Holdt (1965).

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