Thermal Conversions of F\ ightleftarrowsM in Additively Colored KCl Crystals

Abstract

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 F₂ 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\ ightleftarrowsM and from the difference between the dissociation energy of an M center and the jump energy of an F center.