COMPARATIVE ENERGY-LEVEL PARAMETRIZATIONS FOR LANTHANIDE IONS IN OCTAHEDRAL SYMMETRY ENVIRONMENTS

New experimental datasets are presented for the energy levels of tripo sitive lanthanide ions situated in octahedral symmetry environments, i n elpasolite lattices. The freely varying atomic parameters derived fr om energy level parametrizations of the new datasets show empirical re lations with atomic number. The magnitudes of the crystal field parame ters for a given system change considerably, according to the number o f energy levels employed in the fit. This. fitting uncertainty blurs t he trends in the parameters across the lanthanide series. The elpasoli te lattice is a model system for investigating the crystal field pertu rbations experienced by a lanthanide ion when the chemical identity of the nth nearest neighbour in the coordination sphere is changed.