Temporal Behavior of Electron Distributions in an Electric Field

Coefficients are derived for a one-dimensional Fokker-Planck equation describing the evolution of an electron energy distribution. These coefficients include acceleration of electrons between collisions in addition to the collision terms. The coefficient for the average rate of change of the electron energy, $\frac{〈\Delta \epsilon 〉}{\Delta t}$, is the same as obtained with the "average-electron" theory; but the expression for the dispersion, $\frac{〈{\left(\Delta \epsilon \right)}^2〉}{\Delta t}$, has not appeared previously.