Laser-induced line-narrowing ofEu3+fluorescence in fluoroberyllate glass: Site-dependent spectroscopic properties and their structural implications

The techniques of laser-induced fluorescence line-narrowing were applied to the study of the spectroscopy of ${\mathrm{Eu}}^{3+}$ in a KCaAl fluoroberyllate glass. Large systematic changes were observed in the intensities and wavelengths of the various features of the emission and in the decay times of that emission. Using previously developed criteria, the site-dependent behavior of the ${}_{}{}^5{}_{}{}^{}D_{0,1}^{}{}_{}{}^{}$ states and of all Stark components of the ${}_{}{}^7{}_{}{}^{}F_{0,1,2}^{}{}_{}{}^{}$ states were derived; calculations using the electrostatic crystal-field approach were performed and gave a good fit to the observed splittings across the entire range of sites. The structural model derived for oxide glasses was found to be inadequate to explain the observed behavior, but an acceptable alternate model was derived; this model involves a ninefold coordination of ${\mathrm{Eu}}^{3+}$ by two sets of nonequidistant fluoride ions and a systematic axial distortion of this arrangement.