Optical emission spectra and crystal field analysis of Eu3+ in the cubic Cs2NaYCl6 host

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Abstract
Unpolarized and magnetic‐field‐induced circularly polarized luminescence spectra are reported for Eu3+ doped into the cubic Cs2NaYCl6 host. These spectra were obtained at high resolution under variable temperature conditions, and they span the 5DJ(J = 0–3)→7FJ(J = 0–5) transition regions of Eu3+. A detailed analysis of the spectra leads to a nearly complete location and assignment of the crystal field levels split out of the 7FJ(J = 0–5) and 5DJ(J = 0–3) term levels of Eu3+. Essential to the spectral analysis are crystal field energy level calculations and intensity calculations for both the magnetic dipole origin transitions and the electric dipole (one‐phonon) vibronic transitions. The dominant contributions to the vibronic structure in the spectra are assigned to vibronically induced electric dipole transitions which involve coupling between the 4f electrons and the three ungerade vibrational modes localized within the EuCl3−6 chromophoric moiety. Lesser contributions are made by vibronic transitions involving vibrational modes not localized within the EuCl3−6 cluster (e.g., low‐frequency lattice modes). Excellent agreement between theory and experiment is achieved for the luminescence intensities and the magnetic‐field‐induced circularly polarized luminescence spectra associated with the magnetic dipole allowed origin transitions. Very good agreement is also achieved between the calculated and observed vibronic intensity spectra. The latter were calculated using a theoretical model for vibronically induced electric dipole transition intensities which includes contributions from both the static‐coupling and dynamic‐coupling Eu3+‐ligand interaction mechanisms.