Ion implantation has been used to colour LiF crystals at room temperature. Concentrations of the different colour centres (mainly F and F2centres) have been monitored through optical absorption measurements. Ion doses from 5 × 1012to 1016ion cm−2lead to defect concentrations reaching × 10−3of the halogen sites. Measurements at the wavelengths of the F and F2absorption bands have shown an apparent power relation ofF2= KF1.4. This empirical relation is found to hold for all the different implantations used. However, reappraisal of the data, allowing for overlapping absorption features, brings theF/F2kinetics back to the normal relationship ofF2= KF2. TheKvalues are closely related to the electronic stopping power for proton irradiations and vary as E−0.67.