X-ray destruction of impurity-vacancy dipoles in KCl:Eu2+

X-irradiation of KCl:Eu
²⁺
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 The 220 nm 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. To explain these results it is proposed that X-rays increase the rate of aggregation of dipoles, and that it is the cation vacancies bound in I-V dipoles that are converted to anion vacancies which later form F-centers.