Two-photon spectroscopy of europium(III) elpasolites

We present polarized two-photon excitation (TPE) spectra, including Zeeman data, for europium(III) in the elpasolites Cs 2 NaEuCl 6 and Cs 2 NaYF 6 :Eu 3+ . Approximately 80 and 60 levels of unambiguous symmetry have been assigned respectively in each compound up to 32 000 cm -1 with the aid of a one-electron crystal field Hamiltonian. This represents the most complete and extensive data set so far reported for Eu(III) at a cubic site. Comparisons are made between comparable data sets for Eu(III) f 6 and Tb(III) f 8 . Deviations from the predictions of the one-electron crystal field model are discussed in terms of the spin correlation crystal field.