Optical absorption and thermoluminescence of Gd- and Sm-doped CaF2 single crystals irradiated with X-rays

Optical absorption measurements carried out on CaF2: Gd (0.2 mol%) show that it exhibits an absorption band at 272 nm. X-ray irradiation seems to remove this band but produces two absorption bands at 370 and 540 nm, the absorption in these bands increasing with X-ray dosage. CaF2:Sm (0.2 mol%) shows absorption bands at 240, 300, 412 and 630 nm. X-ray irradiation increases the absorption in these bands except in 412 nm which decreases with X-ray dosage. Partial thermal bleaching experiments bring out interesting changes in the absorption bands; when the X-ray-irradiated CaF2:Gd and CaF2:Sm are heated to 3000C, these crystals seem to attein their original absorption characteristics. Thermoluminescence light output of these samples irradiated with X-rays shows peaks at 107, 177, and 277 degC for CaF2:Gd and at 100, 152 and 244 degC for CaF2:Sm. An attempt is made to explain these results. (author)