Optical spectra and crystal field analysis of Dy3+ in Cs2NaDyCl6 and Cs2NaYCl6: Dy3+(5 mol %).

Optical absorption and emission measurements are reported for the Cs2NaDyCl6 and Cs2NaYCl6: Dy3+(5 mol %) systems under variable-temperature (10–298 K) conditions. For both systems, the data are compatible with the retention of octahedral (Oh) site symmetry at the Dy3+ ions over the entire 298 to 10 K temperature range. The only differentiation between the systems is the much greater quantum efficiency of 4F9/2 emission in the doped system vs that in the neat system. Forty-five crystal-field levels spanning 18 multiplets of the Dy3+ 4f9 electronic configuration are located and assigned, and an additional 12 crystal-field levels associated with six other multiplet manifolds are located, but left unassigned. These energy level results are analyzed on the basis of a nine-parameter 4f-electron Hamiltonian operating within a complete Russell–Saunders (SLJ) basis set for the 4f9 configuration of Dy3+. The most intense electric-dipole vibronic lines observed in the optical spectra are assigned to one-phonon vibronic transitions associated with the three odd-parity ‘‘moiety’’ modes of the DyCl3-6 octahedral clusters: ν3(t1u), ν4(t1u), and ν6(t2u). Intensity calculations are reported for both the no-phonon magnetic-dipole (origin) transitions and the one-phonon (ν3, ν4, and ν6) electric-dipole vibronic transitions. [ABSTRACT FROM AUTHOR]