Laser-induced fluorescence line narrowing in Eu glass: A spectroscopic analysis of coordination structure

By means of the techniques of laser-induced fluorescence line narrowing, the emission spectrum of Eu^3+ in a sodium-barium-zinc silicate glass, and the temporal dependence of the emission, were measured as functions of of excitation wavelength. Large variations were observed in the intensities and wavelengths of the various components of the emission. The observed transitions were assigned in terms of a C₂ₕ site symmetry, which was found to give an adequate approximation to the symmetry of the local environment of the ion. Crystal-field calculations were performed and gave a respectable fit to the observed splitting across the entire range of pump wavelengths. A simple structural model is proposed for the behavior of the first coordination shell of the Eu^3+ ion in the glassy matrix. The model involves the progressive approach of a ninth ligand into an originally octacoordinate site, and is consistent with the signs and relative magnitudes of the experimentally derived crystal-field parameters.