Mössbauer data reduction: The M1-E2 transition of 99Ru

A general methodology for the extraction of hyperfine parameters is given for mixed transitions (M1, E2) between 52, 32 Mossbauer nuclei. Rather than approximate the spectrum with a sum of Lorentzian lines, which are compared with theoretical spacings and amplitudes, the fitting is done directly on the controlling hyperfine parameters. The method offers advantages for complex, unresolved spectra and the difficult case of ruthenium (99RuO2) is examined in detail.