F-Aggregate Color Centers in KCl

Abstract

The equilibrium which is established between $F$ and $F$-aggregate centers in KCl by x rays has been studied at room temperature. It was found that the concentration of $R$ centers was proportional to the product of the concentration of $F$ and $M$ centers, indicating that the $R$ centers are composed of three $F$ centers. The concentration of $N_2$ centers was proportional to the product of the concentration of $F$ and $R$ centers suggesting that the $N_2$ center is composed of four $F$ centers. The concentration of $N_1$ centers was proportional to the concentration of $M$ centers suggesting that the $N_1$ center is composed of two $F$ centers. The deviation from linearity of the ${N_F}^2$ versus $N_M$ curve is shown to arise from the presence of higher aggregate centers. Samples x irradiated at room temperature to establish an equilibrium among $F$ and $F$-aggregated centers were cooled and the irradiation continued. The concentration of $M$ centers decreased exponentially with irradiation time. The temperature dependence of this exponential decay time corresponded to an activation energy of 0.07 eV for temperatures above 100°K.