IR luminescence of $\alpha$-Al$_{2}$O$_{3-\delta}$ at 4–300 K

It is established that simple color centers of the $F^+$ and $F$ type (anion vacancies with one or two electrons, respectively) in anion-deficient corundum ($\alpha$-Al$_{2}$O$_{3-\delta}$) crystals can be transformed into complex centers (including divacancy centers of the $F_2$ type) using a special thermo-optical treatment. A fine structure of the photoluminescence bands of complex centers of both the known and unknown natures was recorded in these crystals at helium temperatures in the near-IR range. A comparison with the photoluminescence bands in neutron-irradiated $\alpha$-Al$_2$O$_3$ samples with the initial stoichiometric composition reveals their complete similarity, which indicates the possibility of nonradiative formation of complex centers in $\alpha$-Al$_2$O$_3$.