Fluorescence line narrowing spectroscopy of Eu3+ in a niobium tellurite glass

The relationship between optical properties and local structure has been studied in a niobium tellurite glass of molar composition 4.0Nb2O5–87.0TeO2–8.5Al2O3–0.5Eu2O3 using both broadband and laser-induced fluorescence line narrowing techniques. From the broad band excitation and emission spectra information about the local symmetry and the main lanthanide–ligand vibrational modes of the Eu3+ ions in this matrix was obtained. Under laser selective excitation in the 7F0 → 5D0 inhomogeneous band the site-dependent luminescence of the Eu3+ ions allow us to analyze the distribution of local environments for the lanthanide ion in the niobium tellurite glass. Moreover, the energies of the Stark components of the 7F1 and 7F2 multiplets were obtained as a function of the excitation energy and a crystal field analysis was carried out assuming a C2v site symmetry. From the calculated crystal field parameters Bkq the ratios B22/B20 and B44/B40 for each excitation energy were obtained and compared with the values calculated using the geometric model proposed by Brecher and Riseberg.