X-Ray Expansion and Coloration of Undoped and Impurity-Doped NaCl Crystals

摘要: Expansion and coloration measurements of undoped impurity-doped single crystals NaCl have been made under x-ray irradiation (43 kvp 20 ma) for intervals up to three hours. was measured in a direction normal the beam with sensitive capacitive dilatometer that designed compensate automatically thermal fluctuations. It found initial rate creation $F$ centers exceeds vacancy pairs as computed from expansion data; however, after continued rates $F$-center vacancy-pair production are approximately evenly matched. This suggests results both vacancies originally contained crystal created during irradiation, while later is due essentially process. Within framework this interpretation it possible estimate negative-ion concentration number crystals. ranges 1\ifmmode\times\else\texttimes\fi{}${10}^{16}$/${\mathrm{cm}}^{3}$ Harshaw value larger than 6\ifmmode\times\else\texttimes\fi{}${10}^{17}$/${\mathrm{cm}}^{3}$ calcium-doped grown at NRL. Although presence large explains its enhanced color sensitivity x-rays without corresponding enhancement x-ray-induced expansion, explanation not accord simple expectations charge compensation law mass action.