Photoplastic Effects in Colored KI Single Crystals Containing Potassium Metal Colloids, Mem. Osaka

In order to elucidate the mechanisms of photoplastic effects (PPE) in alkali halide crys-tals containing alkali metal colloids formed owing to the F-center coagulation it is essen-tial to clarify and/or to control the relevant defect spectrum relating to PPE phenomenon. In the electric furnace held at a desirable temperature a densely colored KI crystal plate, prepared by using the electrolytic coloration method, was mounted between the two electrodes kept at high d.c. electric field, e.g., 1000V/cm, as well as was simultaneously il-luminated with the relevant F-band light for 30 min. It was found that by using this simple method,-electro-optical bleaching method-, the concentration of the F-centers in the speci-mens is markedly reduced in comparison with that in the specimens obtained from conven-tional thermal treatment performed so far. A brief discussion is given to the processes concerning the coagulation and reduction of the F-centers coexisting alkali metal colloid particles in the specimens. Key Words: photoplastic effect, colored KI single crystal, potassium metal colloid, electrolytic coloration, electro-optical bleaching metho