Excitonic Processes and Thermoluminescence

Processes of defect creation by nonionizing radiation were studied by applying thermoluminescence methods. KBr crystals were irradiated at 80 K by monochromatic uv light in the region of 1800-2300 Å. Shapes of glow curves were found to differ from those obtained after $x$ coloration. Excitation spectra of the various glow peaks as well as dose dependence of their intensities were investigated. The excitation spectrum showed maxima at the $\alpha$ band and on the long-wavelength tail of the fundamental absorption. Most of the glow peaks showed a linear dose dependence. The mechanism proposed by Pooley and by Hersh is extended to the case of defect creation by irradiation into a perturbed exciton state and excitation of thermoluminescence. An expression for the number of the defects created by the uv irradiation is derived as a function of the radiation dose. This expression takes into account the absorption coefficient of the crystal and, therefore, the penetration depth of the exciting monochromatic light. Experimental results were found to be in good agreement with those predicted by the model.