COLOR CENTERS PRODUCED IN KCl AND KBr BY PROLONGED X-IRRADIATIONS AT LOW TEMPERATURES
Thesis/Dissertation
·
OSTI ID:4013992
Studies were made on the effects of x irradiation of extended duration on the production of color centers in KCl and KBr at low temperatures and possible implications with regard to suggested color center models were examined. An additional problem undertaken was to conduct a search for M centers by x-ray production at low temperatures. Thin plates of KCl and KBr single crystals were exposed to x rays at low temperatures for prolonged times (approximately 60 hours). Irradiations were interrupted periodically for measurements of optical absorption spectra between 200 m mu and 1.5 mu without intervening warm-up. Growth curves were determined at 18 deg K for the F, K, M, and H bands in addition to a new band observed at 245 m mu in KCl and 278 m mu in KBr called the H' band. Likewise, growth curves were observed for the F, K, M, V/sub 2/ and V/sub 4/ bands at 80 deg K. The F to K ratio was found to remain constant indicating that both of the bands arise from transitions in the same center. The concentration of M centers was found to depend quadratically on the Fcenter concentration. This result gives conclusive support that the M center consists of a pair of associated F centers rather than a vacancy pair plus a single F center. The F to H ratio was observed to be constant for short x irradiations supporting the viewpoint that the two centers are produced as complementary defects; however, for prolonged exposures this constant ratio is no longer maintained. The number of F centers is in constant ratio to the combined concentrations of H and H' centers provided that the oscillator strength of the H' band is suitably chosen. The linear dependence of the generation of both H/ sub 4/ centers in KBr and V/sub 4/ centers in KCl on F-center concentration suggests that V/sub 2/ and V/sub 4/ centers, rather than V/sub 1/ centers, are fundamentally related to the mechanism of formation of F centers near liquid nitrogen temperature for a prolonged irradiation. (Dissertation Abstr., 24: No 9, March, 1964)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-18-020668
- OSTI ID:
- 4013992
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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