Energy levels and interaction between Eu3+-ions at lattice sites of symmetryC 2 and symmetryC 3i in Y2O3

Besides the known energy levels of Eu³⁺ at lattice sites of symmetryC ₂ in Y₂O₃, some transitions of this ion at lattice sites of symmetryC _3i in the same host crystal have been found and it was possible to construct the energy level scheme in part. Evidence for an energy transfer from Eu³⁺(C _3i ) to Eu³⁺(C ₂) is given, the strength of which is measured as a function of the Eu₂O₃ concentration. The results lead to the assumption of a fixed distanceR ₀ for the interaction responsible for the energy transfer. A temperature-independent value ofR ₀=8.7 Å was found. The full explanation of the underlying quantum mechanical mechanism requires further experiments.