COLOR CENTERS IN LiNbO₃ CRYSTALS

Color centers stable at room temperature with absorption bands peaking at 365m, 460nm, 540nm and 620nm were produced in LiNbO₃ crystals by γ-radiation, Measurements with XPS (X-ray photoelectron energy spectroscopy) and ESR (electron spin resonance) techniques show that the concentration of Nb⁴⁺ ion is high in the reduced LiNbO₃ crystal but no typical ten-line Nb⁴⁺ ESR spectrum appears. The experimental results can be explained by the Nb⁴⁺ ion-F⁺ center association model.