Moessbauer isomer shifts in chemical systems of gold. Chapter 8b

The 77.3-keV gamma transition in monoisotopic 197Au is well suited for chemical applications of Moessbauer spectroscopy, since the observed ranges of both isomer shifts and electric quadrupole splittings cover several experimental linewidths. The results of isomer shift measurements with chemical components of gold reveal a dependence of the isomer shift on the formal oxidation state similar to the one found in compounds of the 3d, 4d, and 5d transition elements. Furthermore, appreciable variations of the isomer shifts within the same oxidation state were observed for aurous and auric compounds. These variations indicate a marked dependence of the isomer shift on the nature of the ligands. Gold compounds have turned out to be particularly suitable for a study of the correlation between the isomer shifts and the chemical properties of the ligands, since gold - within the same oxidation state - forms many highly covalent 'model' compounds of the same molecular symmetry and with simple ligands. (Auth.)