Ligand polarization contributions to lanthanide 4f → 4f magnetic dipole transition moments and rotatory strengths

Radiation-induced (dynamic) polarizations of electronic charge distributions on ligands may contribute to both the electric- and magnetic-dipole moments of 4f → 4f transitions in lanthanide complexes. These ligand-polarization effects on magnetic-dipole transition moments are examined in the present study, and their possible influence on the rotatory strengths of 4f → 4f transitions in chiral lanthanide systems is given special attention. The ligand-polarization mechanism for magnetic-dipole transition moments is not likely to contribute significantly to the total dipole strengths of 4f → 4f transitions in noncentrosymmetric lanthanide systems. However, this mechanism may contribute significantly (or detectably) to the rotary strengths of certain 4f → 4f transitions in chiral lanthanide systems. The relative importance of these contributions will be greatest for transitions with predominantly |ΔJ|>=2 character and with relatively large Usup(lambda)(lambda=2,4, and 6) matrix elements. (author)