Gas pressure dependence of photon emission accompanying fracture of polycrystalline MgO in nitrogen

The photon emission accompanying fracture of a polycrystalline MgO was investigated at room temperature under N₂ gas pressures from 10 ^-4 to 10⁵ Pa. At fracture, the ultraviolet, visible and infrared photon emissions instantaneously increased, and then rapidly decreased in most of the experimental conditions. However, in a N₂ gas pressure of around 100 Pa, their peak counts lasted for about 10 milliseconds, and the amount of the UV photon emission was fifteen times larger than those obtained in the other N₂ gas pressures. This abrupt increment in the emission was explained by the luminescence due to N₂ gas discharge according to the classical Townsend's theory. In conclusion, the photon emission accompanying fracture of a polycrystalline MgO mainly originated from the excited defects as reported by the authors previously, but the N₂ gas discharge had a supplementary effect on the emission around a specific N ₂ gas pressure.