[en] The electron degradation spectrum, essentially an energy distribution function of an irradiated system, provides a general basis for determining, not only the fate of the incident (or internally produced) radiation, but also for determining the initial or primary yields of the various excited states of the medium. The degradation spectrum thus describes the initial response of the medium to the radiation. This review-type paper focuses on results obtained in calculations for molecular hydrogen gas. The treatment is presented under the following headings: bookkeeping methods; definition of the degradation spectrum; collision data; water vapor; the total ionization cross section; modification of Gerhart's data; sensitivity of the computed degradation spectrum and mean energy per ion pair; initial yields in H₂; spectra of sub-excitation electrons; and spatial distributions. 70 references, 3 figures, 2 tables