VIBRONIC COUPLING AND SINGLE-STEP ENERGY-TRANSFER IN THE SYSTEM NA5(GD, EU)(WO4)4

The luminescence properties of the system Na5(Gd, Eu)(WO4)4 are reported. The intensity of the vibronic sidebands in the excitation spectra of the Eu3+ emission increases with the Eu3+ concentration, whereas in the emission spectra this intensity is concentration independent. This is explained tentatively with a model involving the7Fand charge-transfer states of Eu3+ and the charge-transfer state of WO2-4. Vibrational frequencies are derived from the spectra. Multistep energy migration over the Eu3+ sublattice is not observed in Na5Eu(WO4)4. The luminescence of about 10% of the Eu3+ ions is quenched by single-step energy transfer to acceptors. Single-step energy transfer also occurs from WO2-4 to Eu3+. © 1990 Academic Press, Inc. All rights reserved.