A New ESR Center in X-Irradiated CaF₂ Crystals

Abstract

After thermal-treatment or optical illumination of X-irradiated CaF₂ single crystals, a new ESR signal was observed at room temperature, whose spectrum consists of a single line with g=2.0013±0.0007. Thermal growth of the center was observed in the temperature range between room temperature and 90°C, and its activation energy was determined as 0.43±0.03 eV, while the decay of the center was observed under subsequent thermal-treatment above 80°C, whose activation energy was 0.63±0.03 eV. Optical illumination on the X-irradiated crystals enhanced the ESR center and maximum response was observed at 380 nm over the wavelength investigated. Thermal properties of the ESR center were interpreted in connection with optical absorption and thermal glow.