Anomalous lineshapes in paramagnetic hf split Moessbauer spectra of high spin Fe (III) ions in amorphous frozen solution

The ferric hexaquo complex [Fe(H2O)6]3+ was investigated in a magnetically dilute aqueous solution, frozen to a homogeneous glass by means of Moessbauer spectroscopy. Spectra obtained with various applied magnetic fields up to 6200G at 4.5K show a well resolved paramagnetic hyperfine structure. With small applied fields the lines have an anomalous, asymmetric shape. By comparison of the spectra obtained in small and strong fields it is concluded, that the anomalous shape is not, as hitherto assumed, caused only by the random orientation of the crystal field axes relative to the applied field direction. The shape is ascribed to variations in the crystal field parameters among the complexes in the glass matrix