Mobility of nonequilibrium conduction electrons in air
Abstract
An integrodifferential equation is derived describing the time evolution of the electron energy distribution function in a gas in a transient electric field. A finite difference approximation and a time stepping algorithm using matrixvector techniques are devised to solve the integrodifferential equation. An extensive published cross section set is added to the time stepping algorithm, enabling one to calculate realistic energy distribution functions in air. Also described is a projection method that allows computation of electron swarm properties such as collision volume (inversely related to mobility) using measured data for equilibrium distributions. This projection method is shown to have desirable variational properties in calculating the swarm properties. Compare orthogonal and nonnegative projection methods with conventional techniques for their ability to reduce error in estimates of collision volume arising from cross section induced error in the energy distribution function. A singlevector projection with cleanup of approximation error performs best, leading to significant reduction of collision volume error when the distribution function maximum occurs at not more than about 0.1 eV. Other projections perform poorly compared to conventional methods of calculating swarm collision volume, because of inherent dependence of the projection basis of equilibrium distributions and resulting illconditioning of the projection matrix.
 Publication:

Final Report
 Pub Date:
 June 1990
 Bibcode:
 1990hdl..reptQ....W
 Keywords:

 Air;
 Algorithms;
 Conduction Electrons;
 Electron Energy;
 Electron Mobility;
 Plasma Physics;
 Differential Equations;
 Distribution Functions;
 Electric Fields;
 Electrical Resistivity;
 Errors;
 Finite Difference Theory;
 Integral Equations;
 Nonequilibrium Flow;
 Time Marching;
 Atomic and Molecular Physics