Comparative study on mechanoluminescence of irradiated and non-irradiated ionic crystals.

Effect of surrounding gas on mechanoluminescence (ML) of non-irradiated KCl:Ca2+ and X-ray irradiated one has been investigated in order to clarify the ML due to dislocation movement. For both samples, the ML appears only in the narrow pressure range from 10 to 10(3) Pa with a peak at 133 Pa. Emission spectrum of ML for both samples in Ne gas has indicated a prominent peak at 580 nm that coincides with a strong line of Ne gas. Above results indicate that the observed ML is caused by electric discharge at the crystal surface. Discussion is also made on the effect of Ca2+ on both the ML intensity and the charges carried with dislocations.