F-aggregate centers formation in BaLiF3 crystals

The kinetics of F-aggregate centers formation is investigated in the invert ed fluoroperovskite of BaLiF3 submitted to electron-irradiation. By studies of the changes in the absorption spectra during storage of samples in the dark, at room temperature, it was possible to verify a surprising and inter esting dependence on defect formation with the crystal growth direction. In spite of its cubic structure, crystals grown in the [100] and [111] direct ions and submitted to the same conditions of irradiation, showed in each ca se different species of F-aggregate centers. It was possible, in particular , to enhance the production of a defect absorbing at 630 nm in [100] crysta ls which we believe to correspond to F-2(+)-centers in BaLiF3.