OPTICAL EFFECTS IN NAF CRYSTALS IMPLANTED WITH 100-KEV IONS

Optical absorption spectra are presented for NaF crystals implanted wi th Mg+, Al+, Ar+ and Kr+ ions. Fluences were in the range 6 x 10(15) t o 1 x 10(17) cm(-2). Prominent F and F-2 bands are observed at 341 and at 505 nm respectively; as well as extra bands near 219 and 256 nm, N on-uniform growth of F and F-2 bands with fluence is observed. An intr insic sodium colloid band is observed near 470 nm using rare gas ions. In comparison with LiF, thermal annealing following implantation does not lead to significant development of extrinsic colloids in NaF. Bea m heating during implantation favours low order defect bands (F, F-2) rather than high order aggregates (F-4, colloids).