Vacuum ultraviolet absorption of silica samples

Optical absorption analysis in the ultraviolet and vacuum ultraviolet region from 4.0 to 9.0 eV has been performed on different silica materials. We analysed natural and synthetic silica samples, both as grown and irradiated with different irradiations, neutrons, γ, and ultraviolet photons. Regardless of irradiation we always observed in the spectrum of irradiated samples the growth of the band at 5.8 eV, a band attributed to the E′ paramagnetic center. Comparing this absorption under different irradiation, we suggest the B 2 and E absorption bands are not correlated and therefore cannot be assigned to the same defect.