The excitation spectra of photo- and thermo-luminescence were compared in the VUV - UV spectral region in and scheelite tungstates. Temperature dependences of emission intensities and decay times were measured for in the 80 - 300 K range and approximated by a simple phenomenological model. The energy level structure of the emission centre excited state and related kinetic processes are discussed for both tungstates.

The excitation spectra of the recombination luminescence of YAG single crystals doped with isovalent impurities of Sc and La are studied. The excitation band of the excitons trapped near impurity ions is observed at 6.7 eV, adjacent to the YAG intrinsic absorption edge. The processes of energy transfer and storage as well as their relation to the problem of the origin of the 4.9 eV emission band (supposed to be self-trapped exciton emission) are studied and discussed. The overlapping of the spectral region of direct creation of excitons with the interband transition edge (causing a metastable character of excitons) is shown. The features of relaxation processes are discussed from the viewpoint of the specificity of the electron structure of complex oxides.

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