Dichroism in Additive Colored KCl:OH

Large amount of dichroism in 2.44 ev and 0.84 ev bands with opposite sign is found with [011] polarized F lignt irradiation in additively colored KCl:OH crystal in addition to the pure F–M dichroism. The above dichroism accounts for a large part of the origin of the irregularities in F–M dichroic correlation, which have been frequently observed in KCl crystal, supporting the assumption of higher excited states for the phenomenon. The speed of the growth of the F–M dichroism is very much faster in KCl:OH than in the KCl crystal because of the difference in the optical stability of the F and M centers in those two crystals. Only the F–M dichroism chiefly due to preferential bleaching is induced in KCl:OH crystal with polarized M light irradiation. Complicated photochemical and thermal reactions in the additively colored KCl:OH crystal are observed, which may help the interpretation of the results obtained in the optical experiment on the crystal contaminated with hydroxyl ion up to the present.