Optical absorption spectra of MgO single crystals under shock compression between 50 and 132 GPa

Optical properties of transparent windows at high pressures are of essential importance in dynamic experiments. To investigate the effects of plastic deformation-induced defects on optical transparency of MgO single crystals, real-time absorption spectra are measured via impact experiments and fast multi-color pyrometry. Shock pressure ranges from 50 to 132 GPa. Optical transmission histories are measured in each experiment via an on-board light source generated by shock-wave, from which absorption coefficient alpha is determined as a function of the wavelength lambda. The resultant real-time absorption spectrum ( alpha vs lambda) peaks around 520 nm (similar to 2.39 eV), which blueshifts with increasing pressure. These featured spectra are possibly attributed to defective absorption at defect-centers (color-centers) in MgO single crystals generated by shock-waves. Plasticity-induced defects are most likely responsible for the decrease in transparency. MgO single crystals are not suited to be used as an optical window for thermometric in the visible light spectrum under shock pressures above 129 GPa. Published under an exclusive license by AIP Publishing.