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Photochemically produced color centers in KCl and KBr. Technical report No. 5

Technical Report ·
OSTI ID:6314954
KCl and KBr crystals were exposed to unfiltered quartz mercury arc radiation at 15/sup 0/K. If an OH band was present in the crystals before irradiation, the ultraviolet irradiation produced an optical absorption spectrum similar to that produced by x rays at 15/sup 0/K. The optical absorption spectrum and the changes in the absorption produced by annealing at higher temperatures were measured and compared with the spectra observed during similar annealing of x-irradiated crystals. In KCl the 335 m..mu.. band formed by the uv-irradiation bleaches thermally at 56/sup 0/K as does the 335 m..mu.. H band of x-irradiated KCl. The V/sub 1/ band appears at 56/sup 0/K with the disappearance of the H band. As in the case of x-irradiated KCl, the H band may be partially restored by illuminating the crystal with light absorbed in the region of the V/sub 1/ band. In KBr the 381 m..mu.. band bleaches in steps at 35/sup 0/, 46/sup 0/, 56/sup 0/, and 80/sup 0/K as compared with the 381 m..mu.. H band in x-irradiated KBr which bleaches at 30/sup 0/, 46/sup 0/, 56/sup 0/, and 80/sup 0/K. The V/sub 1/ band appears at 46/sup 0/K and grows at 56/sup 0/K. Illumination in the V/sub 1/ band causes regeneration of the H band as occurs in x-irradiated KBr. In both KCl and KBr the photoproduced H band grows by about 10% at approximately 25/sup 0/K. It is concluded that the H centers bleach thermally by diffusing to and combining with other color centers. Recombination with F and ..cap alpha.. centers annihilates the H centers and leads to the formation of V/sub K/ centers, while recombination with a third center (possibly a positive ion vacancy) results in the formation of V/sub 1/ centers.
Research Organization:
Illinois Univ., Urbana (USA). Dept. of Physics
OSTI ID:
6314954
Report Number(s):
NP-5900331; ON: DE85900331
Country of Publication:
United States
Language:
English