Triboluminescence in sodium chloride

The emission of light due to rubbing or impact of two surfaces (Triboluminescence) has been traditionally studied under visible and ultraviolet spectrum. The current study provides an experimental insight into infrared emission occurring during low velocity impact on common salt crystals. The high speed IR imaging done using a whole field IR camera is first of its kind of measurement that provides experimental verification of IR emission occurring in these events. It was observed that the nature of impact surface and the crystalline structure of the material have a marked role in the IR emission. Of the existing theories that explain the origin of light emission in TL, the model provided by Chapman, that TL is a thermal radiation from high temperature regions, which propagate along with the crack, matches closely with the current experimental observations.