Optical emission spectra and crystal field analysis of Pr3+ in the cubic Cs2NaYCl6 host

Abstract

Unpolarized and magnetic-field-induced circularly polarized luminescence spectra are reported for Pr3+ doped into the cubic Cs2NaYCl6 host. These spectra were obtained at high resolution under variable temperature conditions, and they span the 3P0→3H4, 3H5, 3H6, 3F2, 3F3, 3F4, and 1D2→3H4 transition regions of Pr3+. The crystal field levels split out of the 3H4, 3H5, 3H6, 3F2, 3F3, and 3F4 terms are located and assigned, and an existing controversy regarding the relative locations of the 3P0 and 3P1 term levels is resolved. The spectra obtained on the Cs2NaYCl6:Pr3+ (25 mol %) system are dominated by magnetic dipole origin transitions and electric dipole (one phonon) vibronic transitions which obey octahedral (0h) selection rules. However, these spectra also include weak but persistent features which can only be accounted for in terms of Pr3+ sites with lower than 0h symmetry. A number of weak origin lines are assigned to crystal field transitions which are forbidden in 0h symmetry, and the vibronic intensity distributions observed within certain term-to-term transitions reflect the presence of some lowered site symmetries. The vibronic structure observed in the luminescence spectra is dominated by contributions from transitions involving the ν3(t1u), ν4(t1u), and ν6(t2u) PrCl3−6 cluster (moiety) modes, with lesser contributions being made by two nonmoiety modes with frequencies of ∼40 and ∼60 cm−1.