The effect of ionizing radiation on the 10.6 μm absorption of KCl and NaCl

The optical absorption coefficient measured at 10.6 μm by CO2 laser calorimetry, β(10.6) of KCl and NaCl crystals is found to increase upon irradiation with 60Co γ rays. β(10.6) increases faster than the first power of the F center density and shows an approximately linear dependence on M center density for both materials. An additional low intensity γ irradiation of a KCl sample which breaks up the F aggregate centers without increasing the total damage lowers β(10.6). A subsequent bleaching of the sample partially restores the absorption. Additively colored KCl containing F and F aggregate centers without interstitials also show an increase in β(10.6). Therefore, the increase in absorption at 10.6 μm after irradiation is associated with F aggregate centers rather than Cl0 interstitial clusters. (author)