On the Ce-Mn clustering in CaF2 in which the Ce3+→Mn2+ energy transfer occurs

Energy transfer from Ce3+ to Mn2+, ions in a single crystal of CaF2 co-doped with cerium and manganese ions has been analysed. The spectroscopic data obtained clearly indicate that sensitized luminescence with cerium ions as sensitizers and manganese ions as activators takes place between Ce3+-Mn2+ clusters formed in the crystalline matrix. The number of such clusters was estimated using a simple model in which both ions are treated as two-energy-level systems. Some insight into the possible nature of the Ce3+-Mn2+ complexes as well as of the Ce3+ --> Mn2+ energy transfer mechanism taking place inside them were gathered using Dexter's theory for energy transfer phenomena.