Vacuum referred binding energies of the lanthanides in chloride, bromide, and iodide compounds

A study on Er ³⁺ and Yb ³⁺ luminescence excitation in Cs ₃Y ₂I ₉, Cs ₂NaYBr ₆, Cs ₃Lu ₂Br ₉, YCl ₃, YBr ₃, and YI ₃ is presented. The focus is on determining the energy of the charge transfer band, i.e., the energy needed to transfer an electron from the halide anion (Cl, Br, I) to either Yb ³⁺ or Er ³⁺. Those energies together with published spectroscopic information on other lanthanides in the compounds are used to construct vacuum referred binding energies (VRBE) schemes by employing the chemical shift model. Also, VRBE schemes of seven other halide compounds are constructed based on available spectroscopic data. The systematics in the binding energy at the valence band top and conduction band bottom of the thirteen compounds with changing type of halide and with changing compound composition is discussed.