This section provides a brief survey of research on the luminescent spectra of gas media at high pressure in the visible and near IR spectral ranges with excitation by nuclear radiation and fast electron beams. The results of spectral-luminescence investigations in the UV range, aimed at creation of powerful excimer sources of coherent and spontaneous radiation, are not examined here, but are contained, for example, in the surveys [74, 75].

Research on luminescence provides information about the spectroscopic char­acteristics of transitions, making it possible to ascertain the kinetics of populating and “quenching” of excited states and to estimate the possibility of obtaining laser action at individual transitions. Early stages of investigations of radioluminescent characteristics of condensed and gas media performed before 1964 are considered in the survey [76].

From various methods used in spectral-luminescent investigations, we single out the method of single-photon spectrometry [39, 40, 77, 78], which is based on the counting of single photons and allows analysis of luminescent radiation depending on wavelengths and de-excitation times. Single-photon spectrometry is the basis of the method of subthreshold diagnostics of active NPL media, developed at FEI [79, 80]. Further, we shall briefly examine the most significant studies dedicated to researching the luminescence characteristics of gas media excited by ionizing radiation.