Bleaching of F-type centres in alkali halides. Part 1.—Photobleaching in KCl at room temperature

Abstract

The photobleaching at ambient temperature of F and F₂ centres in potassium chloride single crystals has been investigated using the pulse radiolysis method. Both F and F₂ centres absorb in the F band region(ca. 560 nm at room temperature) and the rate of photobleaching of this band at constant incident light intensity is consistent with two different photolytic processes taking place. In the M band region (ca. 830 nm at room temperature) only the F₂ centre absorbs and here the optical density initially increases and then decreases on photobleaching. Careful analysis of the data in both the F and M regions shows that under the prevailing experimental conditions photobleaching of both the F and F₂ centres follows pseudo-first-order kinetics with rate constants consistent with the following scheme: F[graphic omitted]F₂[graphic omitted] higher aggregate centres? The data have been used to obtain the relative oscillator strengths of the F(F), F₂(F) and F₂(M) bands and the values are compared with other estimates in the literature.