Relation between Eu2+ and Ce3+ f ⇆ d-transition energies in inorganic compounds

Data available on the fd-transition energies of Ce3+, in inorganic compounds are compared with those of Eu2+ in the same compounds. Despite differing charge compensating defects, clear correlation was found. The redshift of absorption, the Stokes shift of emission, the centroid shift of the 5d configuration and the total crystal field splitting of the 5d levels of Eu2+ and Ce3+ all appear to be linearly related to one another. The values for Eu2+ are about 0.7 times those for Ce3+. This implies that spectroscopic properties known for Ce3+ can be employed to roughly predict spectroscopic properties for Eu2+ and vice versa. The findings for Ce3+ and Eu2+ can be generalized to all trivalent and divalent lanthanides.