Electronic Energy Levels and Optical Spectra of Trivalent Lanthanide Ions in Water – Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb

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 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 were determined using line-fitting, and several levels reported by Dieke and Carnall were found to be artefacts. 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 were restricted to these by using room temperature absorption spectroscopy. To conclude, the ground state manifold of each luminescent lanthanide was described, and a new benchmark for lanthanide(III) electronic structure is now available for use across the fields of chemistry.