Rate of Production of Color Centers in KCl and KBr by X-Rays at 78°K

Abstract

Growth rates are presented of the $F$, $F^{\prime }$, $K$, $V_1$, $V_2$, and $V_4$ bands occurring when KCl and KBr crystals are x-rayed at 78°K in darkness and under $F^{\prime }$ light. Under these conditions the concentration of $F$, $F^{\prime }$, $K$, and $V_1$ centers present at any given time of x-ray exposure is found to have two fixed values, dependent only on whether the crystal is in darkness or under $F^{\prime }$ light. The rates of production of these centers are reproducible if the crystals are warmed to room temperature under white light after each x-raying at 78°K. This reproducibility indicates that the imperfections responsible for these centers at 78°K are fully removed and the crystals are restored to their initial condition before x-raying, at least as far as these color centers are concerned. A qualitative discussion of the data is presented.