Laser-Driven Shock Wave-Induced Triboluminescence of an Organic Crystal: Toward a Semiquantitative Study

A novel technique for studying triboluminescence (TL) of organic crystals is proposed. N -Isopropylcarbazole (NIPCz) crystals were fixed onto a glass plate, whose reverse side was coated with a black pigment that was used as a shock-generating layer. A single fundamental pulse from a Nd 3+:YAG laser (1064 nm, fwhm ∼ 10 ns) was irradiated onto the shock-generating layer to generate a shock wave, and this resulted in both crystal fracture and TL from the NIPCz crystals. The TL spectrum was almost the same as the fluorescence spectrum of the NIPCz crystals. The dynamic behavior of the crystal fracture and the transient intensity of the TL were shown to be interrelated with each other. The generation of the TL commenced 200 ns after the laser exposure, and this was reproducible irrespective of the NIPCz samples, indicating that the generation and detection timings for TL are controllable with high accuracy by the present technique. In addition, the TL intensity increased with increasing amplitude of the shock wave, as well as the laser fluence. The results presented here demonstrate that the present method provides novel means of investigating TL phenomena semiquantitatively in a noncontact mode.