Luminescence and Dichroism of F and M Centers in Potassium Chloride

In order to determine the model of the M center, the luminescence and dichroism of additively colored KCl were studied in detail. The polarization factor of luminescence due to M centers excited with polarized light in the F band are P (π/4)=-0.37 and P (0)=-0.17. The F band as well as the M band becomes dichroic by irradiating with polarized light in the M band at room temperature or in the F band at low temperature, and the same quantitative relation exists between the amounts of dichroism in the F and M band for both cases. Above results do not contradict the hypothesis that the second M band overlaps with the F band, and if this assumption is granted, it is concluded from the experiment that the symmetry type of the M center is not C 2 v but D 2 h . The oscillator strengths were found to be 0.65 and 0.53 of that of the F band. If the emission due to M centers excited with light in the F band is assumed to be caused by the resonance transfer from F to M centers, in order to explain the experimental value of transfer probability, the distance between both centers must be less than the order of 10 Å.