Photostimulation studies in pure and Li-doped alkali halides

Room temperature X-rayed single crystals of KCl and KCl:Li are subjected to photostimulation (PS) at liquid nitrogen temperature (LNT) with light corresponding to their F-band (F-light). Out of the six and seven monochromatic thermoluminescence (MTL) glow peaks of X-rayed KCl and KCl:Li crystals, only four and six glow peaks, respectively, are found to be stimulable with F-light. A similar experiment is made with pure and Li-doped KBr crystals, X-rayed at -50deg C and F-stimulated at LNT for 15 s. Out of six MTL glow peaks both in KBr and KBr:Li, two and four MTL glow peaks, respectively, are found to be stimulated with F-light as LNT. The different photostimulated MTL peaks are attributed to shallow F- and F'-centre traps filled either by the capture of photo-electrons from the conduction band or through electron tunneling from an excited state F-centre to a neighbouring F-centre. The apparent differences in pure and doped system with regard to photostimulation are attributed to the incorporation of Li-ions in the lattice. (author)