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Title: The optical effects of electron irradiation in crystalline sodium bromide
Author: Calverd, Alan Morris
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1971
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Experimental procedures are described for the reproducible preparation and electron-beam irradiation of single crystal specimens of deliquescent alkali halides, and for the measurement of absorbed dose in the samples to + 1% repeatability. Subsequent measurements of optical density, to ± 1%, at wavelengths known to within 5 nm (at 500 nm), w ere used to plot F band growth/dose curves for several alkali halides, with beam energies between 115 and 460 keV, at room temperature and at 77 K. Cathodoluminescence was measured during irradiation and the luminescent peak wavelengths were located to within +_ 2 nm at 200 nm. Studies with a microscope and microdensitometer produced coloration/depth profiles which were used in conjunction with the optical density/dose measurements to determine the concentration of F centres produced in NaBr samples by irradiation. Studies of the effects of optically or thermally bleaching the F band on the absorption spectrum of NaBr led to the discovery of a series of V bands that had not previously been reported. A study of the detailed kinetics of the iadiolytic coloration of • NaBr showed that at 77 K the growth curve was divided into two distinct saturating phases separated by a plateau whose "height" and "length" depended on the sample purity and beam energy respectively. At room temperature the growth curve had no inflection and a higher saturation value. The final saturation concentration of F centres at a given temperature was found to be independent of the beam energy between 230 and 460 keV and the rate of production of F centres per unit dose was independent of the beam flux. Theoretical and experimental studies of the variation of electron - penetration depth with energy showed that the coloration penetration law differed significantly from that found by. other workers at low er beam energies. The effective coloration depth p(micrometres) in NaBr 1 08 was given by p = 0. 77V ' where V is the beam energy in keV. A beam orientation dependence of p was found for NaCl. F or beam - A /l - energies ^ 2 3 0 k eV it was found that irradiation enhanced the deliquescence of NaBr, presumably by ejecting Br from the surface, but this effect was not detected for beam energies.
Supervisor: Not available Sponsor: Central Electricity Generating Board ; Economic and Social Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics