Mössbauer Effect Studies on Eu151 in Mixed Oxide Structures

In an effort to obtain more nearly monochromatic Sm151 sources for Eu151 a study of the effect of crystal structure on absorption linewidth was undertaken. The broadest lines were found for ternary oxides of presumed high crystal symmetry, such as EuCrO3, while the narrowest lines were found for the soft, asymmetric anhydrous EuCl3. In the case of Eu2Ti2O7 quadrupole splitting was observed corresponding to 1.30 ± 0.04 for the ratio of the quadrupole moments of the excited and ground states and with a value of 1.00 ± 0.02 mm/sec for Γ. The measured quadrupole coupling constant was -280 ± 7 Mc/sec. Absorption efficiencies were found, as expected, to be greatest for the most rigid crystals and least for the soft ones. Isomer shifts were found to vary in order of intuitive “ionicity,” but in some cases the correlation was much better with mass than with electronegativity.