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Publication costs assisted by Fuji Photo Film Co. Ltd.A novel series of crystalloluminescent organic materials is discovered. The binary mixture of a nonconjugated ketone and acetonitrile or AvY-dimethylacetamide emits blue-white light pulses on crystallization at 77°K. The experimental conditions for effective emission are described. The experimental facts suggest the excitation mechanism that the emission phenomenon is essentially triboluminescence, brought about by strain energy in the mixed crystal. The crystalloluminescence spectra were recorded photographically with the use of a continuous interference filter. The emission spectra, with the maximum at about 460 nm, are able to be replaced by different spectra by the addition of a small amount of appropriate sensitizers. The mechanism of the emission process is elucidated by comparing the crystalloluminescence spectrum with photoluminescence spectra. In the absence of sensitizers, the crystalloluminescence emission comes from the lowest excited triplet state of the nonconjugated ketones, while with doped sensitizers, the triplet energy transfer takes place from the ketone to the sensitizers, the triplet states of which are responsible for the observed emission.

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