Hyperfine interactions at europium sites in oxide glasses

The shape of the gamma resonance absorption peak of the Eu3+ ion in a disordered structure was investigated in some phosphate, berate, and silicate glasses by using Eu-151 Mossbauer spectroscopy. The quality of the fits was tested by using the Durbin-Watson d statistics. The observed full width at half maximum of the peak was resolved in a contribution of the broadening and a contribution of the quadrupole splitting, due to the distortion of the Eu site compared to a cubic symmetry. The Eu-O bond was found to have a covalent admixture with 6s character. The axial component of the electric-field gradient at the Eu site was found to be correlated with the optical basicity of the glass.