Luminescence spectra at bending fracture of single crystal MgO

Luminescence at bending fracture of single crystal MgO is investigated. Emission bands at about 400–500 and 730 nm are observed in the fractoluminescence spectra. The former emission decays within several microseconds while the latter decays in several hundreds of microseconds. By comparing with the result of photoluminescence, the 400–500 nm band in the fractoluminescence should be assigned to an intrinsic defect center, while the 730 nm band is due to Cr3+ impurity.