Formation of radiation defects in iron-doped quartz crystals

Studies of the optical absorption spectra were carried out in the visible, UV, and IR ranges to reveal the specific features of the formation of radiation defects in γ-irradiated (the dose ranges 103-109 rad) synthetic crystals doped with iron (0.3x10-3 wt %). By analyzing the experimental dependences of the absorption band intensities on the radiation dose, it was found that the process of the formation of radiation defects in the above-mentioned crystals correlates well with the following pattern. At low doses ≤105 rad, the E4 holes serve as electron traps (an intense absorption band appears at 225 nm). With an increasing radiation dose, the electron migration from shallow to deep traps becomes dominant, which results in a nonselective absorption in the UV range. This is accompanied by the formation of the amethyst color centers (Fe4+) and the migration of alkali ions away from the initial paramagnetic centers (Fe3). The pattern provides a detailed description of the formation of radiation defects and can serve for predicting the properties of crystals under irradiation