New particle physics experiments, space missions, development of novel high power femtosecond short-wavelength laser sources (free electron lasers), advances in medical imaging (PET) and homeland security field require new materials for transformation of high-energy radiation and particle fluxes into photons of a visible-UV range. The creation of new efficient scintillating detectors is impossible without the understanding of the physical processes that determine the conversion of the high-energy radiation into the light. Therefore, the present project is aimed at a comprehensive study of the factors affecting the efficiency of energy transfer to the luminescence centers in series of oxide-based ionic-covalent insulating crystals. Thermalization and localization of multiple electronic excitations created under high-energy irradiation result in the formation of metastable electronic states in the bandgap, which are responsible for luminescence and charge carrier trapping. These final stages of the relaxation of electronic excitations will be studied in details using the method of luminescence spectroscopy. For successful accomplishment of the aims of the project the modern experimental facilities for luminescence spectroscopy in UU, VUV and X-ray spectral regions will be used including the equipment installed at the synchrotron radiation sources in DESY, KSRS and MAX-IV. The theoretical background of the project including calculations of the band structure and optical properties of inorganic insulators will be provided in terms of the network of long-termed and successful collaboration with the highly experienced theoretical groups. As a result of the project the expertise in the study of the complex processes of energy relaxation in advanced oxide-based materials will be built. The project will have a strong impact on research and development in the field of scintillator physics in Estonia.