Surface-roughness–induced electric-field enhancement and triboluminescence
The separation of solids in adhesive contact, or the fracture of solid bodies, often results in the emission of high-energy photons, e.g., visible light and X-rays. This is believed to be related to charge separation. We propose that the emission of high-energy photons involves surface roughness and surface diffusion of ions or electrons, resulting in the concentration of charge at the tips of high asperities, and to electric-field enhancement, which facilitate the discharging process which result in the high-energy photons. If the surface diffusion is too fast, or the separation of the solid surfaces too slow, discharging starts at small interfacial separation resulting in low-energy photons.