Thermal Conversions of F\ightleftarrowsM in Additively Colored KCl Crystals

The composition and decomposition of M centers in additively colored KCl crystals have been examined by the thermal procedures. When a crystal is kept at a temperature between 320°K and 480°K after quenching from about 870°K or after F light irradiation at room temperature, to produce excess M centers, the growth or bleaching of the M band is found to proceed in accordance with a bimolecular reaction, by which the F 2 model of the M center is supported. From the rate constant of the reaction the mean activation energies for the jump of an F center and for the dissociation of an M center are obtained as 0.94 ev and 1.11 ev, respectively. The binding energy of an M center is estimated as 0.18 ev from the mean value of those obtained from the temperature dependence of the thermal equilibrium constant for \(F{\rightleftarrows}M\) and from the difference between the dissociation energy of an M center and the jump energy of an F center.