Jonathan R. G. Thorne

Two-photon spectroscopy of europium(III) elpasolites

We present polarized two-photon excitation (TPE) spectra, including Zeeman data, for europium(III) in the elpasolites Cs2NaEuCl6 and Cs2NaYF6:Eu3+. 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) f6 and Tb(III) f8. Deviations from the predictions of the one-electron crystal field model are discussed in terms of the spin correlation crystal field.

Spin-correlated crystal field analysis of lanthanide elpasolites

Abstract Using extensive two-photon spectroscopic data sets for the lanthanide ions Sm(III), Eu(III) and Tb(III) at cubic sites, we report the results of spin-correlated crystal field (SCCF) analysis. We show these calculations to be consistent with the chemical expectations of radial wavefunction expansion and charge transfer.

Evidence for a spin-correlated crystal field - two-photon spectroscopy of thulium III in the elpasolite Cs2NaYCl6:Tm

We present two-photon excitation spectra for thulium III in the elpasolite Cs2NaYCl6:Tm. 37 out of the total of 40 crystal-field (CF) levels have been assigned, with the aid of a one-electron CF Hamiltonian, representing the most extensive data set so far reported for Tm III at a cubic site. Deviations from the predictions of the one-electron CF model are unusually large, the effective fourth-rank CF parameter being 60% larger for the singlet states than for the triplet states. This is discussed in terms of a spin-polarized covalency that is more pronounced in the singlet states of the metal ion.

Two-photon spectroscopy of samarium(III) in the elpasolite Cs2NaYCl6:Sm3+

We present polarized two-photon excitation (TPE) spectra for samarium(III) f5 in the elpasolite Cs2NaYCl6. Approximately 80 levels have been assigned up to 29 000 cm-1 with the aid of a one-electron crystal field Hamiltonian, representing the most complete and extensive data set so far reported for Sm(III) at a cubic site. Deviations from the predictions of one-electron theory are discussed in terms of the spin correlated crystal field (SCCF).

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.

Inter- and intra-configurational transitions of europium (II) in Ba2Mg3F10

An optical investigation of the properties of europium (II) ions introduced in Ba2Mg3F10 single crystals is presented. The spectra and time-dependence of both the inter-configurational (f–d) and the intra-configurational (f–f) transitions are described. The emission spectrum consists of two emitting Eu2+ centres, each showing one broad f–d band and one 6P7/2 quartet. The thermal equilibrium between the f–f and f–d emitting states is investigated and found to take place on a microsecond timescale for one of the two Eu2+ centres. The spectroscopic results combined with numerical modelling of the influence of the host crystal on the 6P7/2 energy scheme allow the assignment of each f–f and f–d emission to its corresponding Eu2+ centre.