Correlation between absorption bands and implanted alkali ions in LiF

Defects induced in LiF by bombardment with alkali ions in the 1 MeV energy range have been investigated by optical absorption measurements. Inaddition to the absorption bands of F and F-aggregate centres, newbands have been obtained after thermal annealings and have been attributed to implanted ion centres. The corresponding absorption band positions depend on the nature of the implanted ions and have been obtained at 520 nm for sodium (CA(Na+) band) and 680 nm for potassium (CA(K+) band). The comparison of these band positions with those of the colloidal centres created in NaCl and KCl by ionbombardment suggests that they are colloidal bands. So it has been deduced from Doyle's theory that the CA bands were due to the plasma resonance of quasimetallic particles formed after precipitation of the implanted ions.