Hardening of KCl by Electron and Gamma Irradiation

Measurements of the flow stress and F-band coloration have been made at room temperature on a number of different samples of KCl as a function of gamma and electron irradiation. The rate of increase of flow stress with irradiation is found to be greater (or smaller) in those samples and for those irradiation conditions for which the coloring rate is greater (or smaller). Moreover, the flow stress increase in any set of samples is proportional to the square root of the F-band absorption. The implication is that hardening is caused either by F centers or other defects whose production is related to the production of F centers. Since bleaching of F centers does not produce any softening, and since the magnitude of the hardening is of the order of magnitude to be expected for interstitial type defects, the conclusion is drawn that the increase of flow stress due to irradiation of KCl is caused by interstitial Cl atoms or interstitial clusters.