Ionizing radiation in dielectric and optically transparent silica as well as thin SiO2 layers produces defect luminescence as well as charge storage. A comparison of different excitation–relaxation processes like cathodoluminescence, charge injection and trapping, secondary electron field emission, and exoelectron emission leads to a generally similar excitation dose behaviour described by an electron beam saturation dose of 0.01–0.1 C/cm2. This suggests a correlation of these four electron excitation mechanisms likely related to the same kind of defect in glassy SiO2, the 2-fold-coordinated silicon Si: centre with typical electronic singlet–singlet and singlet–triplet transitions according the Skuja model.