Luminescence and radiation-induced color centers in anion-defective alumina crystals after high-dose irradiation

• PL and PLE spectra of the alumina crystals exposed to high doses were measured.
• Aggregate F2-type centers are responsible for an additional PL band.
• The PL of aggregate centers is accompanied by a decreasing intensity of F+- band.
• F+-centers cause formation of charged aggregate color centers.
• F-centers are not engaged in creation of aggregate centers.

A method of UV spectroscopy was used to measure photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra in anion-defective alumina crystals exposed to high doses of gamma-radiation. An additional emission band in the range of 1.6–2.75 eV appears in the exposed crystals. Aggregate F2-type centers in different charge states are responsible for this band. It was found that growing intensity of PL aggregate centers occurs at doses corresponding to saturation of dose response and is accompanied by a sharp drop in the intensity of F+-band in the PL spectrum resulting from combination of F+-centers into aggregates. Uncharged F2-centers are formed when electrons are trapped by F2+ and F22+-centers. The main role of F+-centers in radiation-induced transformations of color centers under high-dose irradiation of anion-defective alumina crystals was indicated.