Study of the Thermal Kinetics of theF′−to−FConversion in KCl by Electron Spin Resonance

The temperature dependence of the $F^{\prime }-\mathrm{to}-F$ conversion has been studied in additively colored KCl, at a number of temperatures at which the $F^{\prime }$ center is thermally unstable. The conversion was monitored by observing the increase of the ESR signal of the $F$ center. The data were analyzed in terms of a kinetics which allowed the electron on leaving the $F^{\prime }$ center to go to a vacancy to form an $F$ center or to an $F$ center to form another $F^{\prime }$ center. The results of the analysis indicate that the half-life of the $F^{\prime }$ center is dependent on the concentration of the $F^{\prime }$ centers. An activation energy of 0.53 ± 0.05 eV was deduced for low concentrations of $F^{\prime }$ centers, where it is indicated that the half-life is independent of the concentration of the $F^{\prime }$ centers.