LiF crystals irradiated with 150Â MeV Kr ions: Peculiarities of color center creation and thermal annealing

Thermal annealing of irradiated LiF crystals with Φ ⩾ 1013 ions/cm2 at 400 K leads to a decrease of F centers (due to annihilation with H centers) and an enhancement of complex Fn color centers (neutral and charged) due to interaction with thermally activated anion vacancies. Annealing LiF crystals at higher temperature (T ⩾ 400 K) leads to a decrease both of F centers and Fn centers. In the annealing process up to 480 K the F2 and F3+ centers are dominating until their reduction above 590 K. At temperatures above 740 K mainly small Li and trace element (Mg, Na) colloids are present in the absorption spectrum. The role of anion vacancies on color center creation and annealing is discussed.