Electronic energy levels and optical spectra of trivalent lanthanide ions in water – Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), and Yb(III)

Chemistry is—in essence—our collective understanding and language describing the electronic structure of each element in the periodic table. For the f-block ions, Dieke diagrams have formed the basis when describing electronic structure. Dieke reported numerical values of the electronic energy levels in his book from 1968, and Carnall reported multiplet energies for the lanthanide(III) ions in water in a series of papers from the same year. The experimental methods have improved since, and in this work, we present a new Dieke diagram for the trivalent lanthanide ions in water. With optical spectroscopy, in particular luminescence spectroscopy at cryogenic temperatures, the electronic energy levels are determined using fitting, and several levels reported by Dieke and Carnall are found to be artifacts. Further, the new methods allow both determination of speciation and description of electronics states and lines. This is in contrast to the bands and multiplets considered by Carnall, who was restricted to multiplets by using room temperature absorption spectroscopy. To conclude, the ground state manifold of each luminescent lanthanide is described, and a new benchmark for lanthanide(III) electronic structure is now available for use across the fields of chemistry.