Optical absorption and thermoluminescence of bismuth-doped NaCl single crystals irradiated with X-rays

The optical absorption in the wavelength range 200 to 800 nm of Bi-doped NaCl single crystals (0.08 and 1.3 mol%) before and after X-ray irradiation for different times, has been measured. The partial thermal bleaching characteristics of NaCl:Bi (1.3 mol%) irradiated for one hour have been studied. The thermoluminescence (TL) curves of the doped samples irradiated for one hour have been recorded. These measurements indicate conversion of Bi3+ to Bi2+ in the doped samples with X-ray irradiation; however, when NaCl:Bi (1.3 mol%) is X-ray irradiated for larger times than one hour, Bi+ and Bi0 seem to be formed also. An attempt is made to understand the results of the present investigations. (author)