Non-radiative energy transfer in lanthanide materials

This lecture emphasizes three principal aspects. First, it examines shielding effects arising from the filled 5s and 5p subshells in multipolar energy transfer mechanisms—namely dipole–dipole, dipole–quadrupole, and quadrupole–quadrupole interactions—between lanthanide ions and ligands. In contrast, for the short-range exchange mechanism, explicit shielding factors are unnecessary, as they are inherently incorporated into the 4f–4f overlap integrals of the interacting valence shells. Second, a novel approach for treating the Judd–Ofelt Ωλ intensity parameters is introduced, based on the thermal root-mean-square displacement around each coordinating atom. This model may contribute to a more consistent rationalization of 4f–4f transition intensities and ion–ion energy transfer processes, particularly when lanthanide ions occupy centrosymmetric sites. Third, it highlights that the quadrupole–quadrupole mechanism can predominate at ion–ion separations up to 20 Å, provided shielding effects are properly considered. Spectral overlap integrals are derived analytically, and intramolecular energy transfer mechanisms in lanthanide coordination compounds are discussed.