Franck–Hertz effect in cathodo- and photoluminescence of wide-gap materials

A brief overview of previously obtained and novel data on the manifestations of an analogue of Franck–Hertz effect in photo- and cathodoluminescence of wide-gap inorganic materials is presented. On the example of NaCl:Tl+ and MgO:Cr3+ single crystals, the excitation processes of the luminescence of 6s2 Tl+ ions and 3d3 Cr3+ ions by 5–15 keV electrons or 5–20 eV photons at 6–420 K have been studied. The rapid processes of the direct energy transfer to Tl+ by hot conduction electrons or to Cr3+ centers by hot electrons and/or hot valence holes have been separated from rapid excitonic and more inertial electron–hole processes.