The natures of the stable and transient colour centres in these crystals were studied. The centres were created by exposing them to various types of radiation in the visible and ultra-violet ranges.

Radiation Defects in Oxide Crystals Doped with Rare Earth Ions. A.Matkovskii, A.Durygin, A.Suchocki, D.Sugak, F.Wallrafen, M.Vakiv: Radiation Effects and Defects in Solids, 1999, 150[1-4], 591-5