F and F2 centres in LiF induced by ion implantation

Ion implantation has been used to colour LiF crystals at room temperature. Concentrations of the different colour centres (mainly F and F 2 centres) have been monitored through optical absorption measurements. Ion doses from 5 × 10 12 to 10 16 ion cm −2 lead to defect concentrations reaching × 10 −3 of the halogen sites. Measurements at the wavelengths of the F and F 2 absorption bands have shown an apparent power relation of F 2 = KF 1.4 . This empirical relation is found to hold for all the different implantations used. However, reappraisal of the data, allowing for overlapping absorption features, brings the F/F 2 kinetics back to the normal relationship of F 2 = KF 2 . The K values are closely related to the electronic stopping power for proton irradiations and vary as E −0.67 .