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Author Bron, W. E. ♦ Heller, W. R.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword METALS, CERAMICS, AND OTHER MATERIALS ♦ ABSORPTION ♦ BLEACHING ♦ CAPTURE ♦ COLOR ♦ CRYSTALS ♦ DEFECTS ♦ DISTRIBUTION ♦ ELECTRIC CHARGES ♦ ELECTRONS ♦ F CENTERS ♦ IONS ♦ IRRADIATION ♦ LATTICES ♦ LIGHT ♦ MATHEMATICS ♦ MEASURED VALUES ♦ MECHANICS ♦ PHOTOELECTRIC EFFECT ♦ PHOTONS ♦ POTASSIUM CHLORIDES ♦ RADIATION EFFECTS ♦ SPECTRA ♦ STABILITY ♦ TRAPS ♦ VACANCIES ♦ X RADIATION
Abstract Measurements were made on the changes in the bleaching rate of the F band as the result of varying the intensity of F light. Bleaching was done on KCl crystals that were irradiated at room temperature with hard x rays into either the first or second stage of coloration. In the first stage irradiated crystals, the total bleaching of the F centers during the first ten seconds of illumination varied approximately linearly with light intensity at low intensities but became saturated at intensities greater than 5 x 10/sup 14/ photons/sec cm/sup 2/. The bleaching process was thought to occur primarily through the capture of photoelectrons at pre-existing electron traps. Based on this model it was possible to set up the kinetic equations for the bleaching process. Using reasonable values for photoelectron capture coefficients forced the conclusion that the number of photoelectrons war always very small throughout the bleaching process. The resulting simplification in the analysis of the kinetic equations led to a prediction of the experimentally observed variation of the initial bleaching rate with light intensity. The analysis showed that the ratio of the capture coefficient for photoelectrons of the electron trapping centers to that of negative-ion vacancies was about unity, which strongly suggested that the trapping centers were either traps with net positive charge or were neutral traps located close to the original F centers. The rate of bleaching during the second stage of bleaching saturated at the lowest intensity used, which was about 1 x 1O/sup 14/ photons/sec cm/sup 2/. This result is discussed in terms of the analysis given for the first stage of bleaching. (auth)
ISSN 0031899X
Educational Use Research
Learning Resource Type Article
Publisher Date 1960-09-15
Publisher Department International Business Machines Research Center, Yorktown Heights, N.Y.
Journal Physical Review
Volume Number 119
Organization International Business Machines Research Center, Yorktown Heights, N.Y.


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