Time-dependent aspects of electron degradation: Pt. 1

We present an analysis of the kinetic competition between the moderation of subexcitation electrons in a background gas and the excitation of impurity molecules. The central element of our method is the energy distribution of subexcitation electrons as a function of energy and time. The distribution obeys a linear partial differential equation of the first order, which is in general analytically solvable. The analysis is applied to He and Ne gases admixed with N2, as studied by Cooper, Denison, and Sauer in their pulse radiolysis experiments. The temporal behavior of N2 fluorescence, calculated from our analysis, agrees with experiment. The present treatment is an example of a general theory, which represents an extension of the Spencer-Fano theory to time-dependent cases. (author)