EXCITON AND RECOMBINATION PROCESSES IN YAG CRYSTALS

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.