Mössbauer Spectroscopy of Gold Compounds

Mössbauer spectra at 4.2°K were taken with ¹⁹⁷Au in several aurous and auric compounds. For each oxidation state a linear correlation was observed between the isomer shift (IS) and the quadrupole splitting (QS). Both the IS and QS varied over wide ranges in both auric and aurous compounds. Neither IS nor QS alone could be used to determine the oxidation state, but together they appear to determine it uniquely. The results for linear aurous and square‐planar auric complexes are interpreted in terms of $\text{6s6p}$ and ${\text{5d6s6p}}^2$ hybridization, respectively, with varying degrees of ionic character. Attempts to interpret the results quantitatively in terms of the atomic parameters ${\psi }^2\mathrm{(O)}$ and ${\mathrm{〈r}}^{\text{−3}}〉$ were only partially successful: It was not possible to reproduce the large experimental values for ${\mathrm{〈r}}^{\text{−3}}{〉}_{\text{6p}}$ using free atom theory. The nuclear factor was determined as $\text{δR\hspace{0.17em}/\hspace{0.17em}R\hspace{0.17em}=\hspace{0.17em}+\hspace{0.17em}(2.5\hspace{0.17em}±\hspace{0.17em}0.6)}$ using the simple hybridization model.