Photostimulated Thermoluminescence in Potassium Chloride Single Crystals

Thermoluminescence photostimulated over the spectral range 230-1000 m{μ} is investigated in KCl single crystals in the temperature range 90-270^∘{}K. The glow peaks are stimulated by rigorously monochromatic light of wavelength corresponding to the F, to the L, and to the tail of the K band. No V band stimulation is found; only electron traps are therefore involved in the process. Comparison of our stimulation spectra with the corresponding absorption and photoconductivity curves found by other authors shows that, besides the usual trapping through capture of photoelectrons from the conduction band, a second process takes place, namely tunneling from excited F centers; this happens for the glow band centered at {~}215^∘{}K. The trap giving rise to the above band is assigned to F^' centers, according to other works; further evidence is presented to support this identification.