Time-dependent aspects of electron degradation. II. General theory

The well-known Spencer-Fano theory of electron-degradation spectra treats time-independent cases, in which the medium is subjected to stationary irradiation. We present a generalization to time-dependent cases, showing how to calculate the temporal behavior of the electron-degradation spectrum and of related quantities such as the yield of ions or excited states that are produced under nonstationary irradiation. The generalized theory indicates new aspects of electron-degradation phenomena, which are basic to radiation physics and chemistry as well as to applications such as gaseous electronics, upper-atmospheric physics, and astrophysics.