Analysis of (7F0)Γ1g→(5D2)Γ5g, Γ3g and (7F0)Γ1g→(5L6)Γ1g, aΓ5g two-photon absorption spectra of Cs2NaYF6:Eu3+

The direct calculation of transition line strengths and relative intensities is presented for two intraconfigurational two-photon absorption (TPA) transitions of Eu3+ in the cubic Cs2NaYF6 host. Crystal field wavefunctions were utilized for the initial and final fN-electron states and various approaches were used in constructing all the 4fN-1 5d1 intermediate-state wavefunctions. The calculated relative intensities of the (7F0) Γ1g→(5D2)Γ5g, Γ3g TPA transitions are in reasonable agreement with experiment. The neglect of J-mixing in the initial state has only a small effect upon the calculation, whereas the neglect of spin-orbit couplings within the initial and terminal states drastically reduces the calculated transition linestrengths, but does not markedly change the intensity ratios. In the case of the (7F0)Γ1g→(5L6)Γ1g, aΓ5g transitions, serious discrepancies between experiment and theory are found if the intermediate states are constructed from a 4f5 core comprising free ion states and the 5d1 crystal field states. Satisfactory agreement is, however, found when the 4f5 crystal field states are utilized in constructing the intermediate states. The contributions to the transition moment have been evaluated for various Hamiltonian terms and the results are discussed. (author)