Investigation of structural questions on europium compounds by means of 151Eu Mössbauer spectroscopy

151 Eu Mössbauer spectroscopy permits the determination of the symmetry of the site in which Eu is accommodated. It has been shown that the 151Sm F3 source can be considered a monochromatic source. This source was used to measure the line width of Eu3+ in a site with cubic symmetry, i. e. in a Cs2NaEuCl6 crystal. The isomer shift of commercial compounds used as standards (anhydrous EuF3 and EuS) was also measured. In the case of Cs2NaEu(N O2)6 hexanitritoelpasolite the trivalent europium ion is accommodated in a site with perfect cubic symmetry. In Eu(PO3)3 crystalline metaphosphate, the rare earth is located in a site which appears to be distorted with respect to cubic symmetry; this site has no threefold or fourfold symmetry axis.