Evidence of Sixfold Coordination of Nd3+ in Barium Rubidium Silicate Glass

Recent low-temperature spectroscopy and spectral analysis by Robinson and Fournier have shown that Yb3+ is sixfold coordinated in silicate glass at a site of near octahedral symmetry. A similar analysis is reported for Nd3+-doped barium rubidium silicate glass. The absorption and emission spectra associated with the J multiplets of the I2 term have been examined for the most part at low temperatures. The energies of the five Kramers doublets in the I9/24 multiplet have been fitted to the octahedral crystal field calculations of Lea, Leask, and Wolf, and parameters A4〈r4〉 = 337 and A6〈r6〉 = 25 cm−1 were obtained. These parameters predict the energy separations of the two bands in the I11/24, 4I13/2, andI15/24 multiplets and the energies of the lower Kramers doublets in the I15/24 multiplet thus indicating that the Nd3+ is also in a site whose symmetry approached octahedral.