X-RAY-EFFECTS ON CATION IMPURITY-VACANCY PAIRS IN KCL-EU2+

X-ray irradiation of KCl: Eu2+ at room temperature destroyed impurity-vacancy (I-V) dipoles, converted the doubly valent impurity ion to a singly valent state, and created defect centers, e.g., F centers and a 220-nm optical-absorption band. Eu+ produced by the irradiation was observed to grow in proportion to the destruction of Eu2+. The 220-m band was also observed to grow approximately in proportion to the height of the F band, in agreement with previous workers. The number of dipoles destroyed was equal to or exceeded the sum of the number of converted ions and the number of F centers produced. A possible explanation of these results is that x rays increase the rate of aggregation of dipoles. It is likely that it is the cation vacancies bound in I-V dipoles that are converted to anion vacancies which later form F centers. © 1979 The American Physical Society.