Host dependence of the rare-earth ion energy separation 4f N–4f N−1 n l

Abstract

The interaction between two 4f electrons in a rare‐earth ion by means of the polarization of a ligand in a solid is discussed. It is shown that this interaction gives rise to a host dependent shift of the energy separations between the 4f ^N and 4f ^N−1 nl configurations. The results of the theory of these energy shifts are compared to experimental data for Nd³⁺, Er³⁺, and Tm³⁺ in the hosts YF₃, LuF₃, LiYF₄, and LaF₃. Also a shift in the Slater integrals and the spin–orbit parameter is predicted by the same interaction.