Improved computational procedure for evaluation of overlapping hyperfine parameter distributions in Mossbauer spectra

Abstract

An improved method for computer analysis of Mossbauer spectra in terms of hyperfine parameter distributions is presented. The method evaluated by Phillips and Twomey (1962) is extended to include an additional constraint on the endpoints of the distribution function, and this algorithm is combined with an iteration procedure. This application of the method is illustrated in fitting a spectrum with a distribution in magnetic hyperfine fields using the iteration procedure to obtain directly from the spectrum values for the isomer shift, quadrupole interaction and line area ratios. The method is also used to determine the Fe2+/Fe3+ ratio from a paramagnetic spectrum with broadened non-Lorentzian lines. To obtain this an average correlation between isomer shift and quadrupole splitting has been assumed for iron in each of the two valence states. It is shown that spectra originating from symmetric distribution functions can be fitted equally well assuming either of two different correlations between isomer shift and quadrupole splitting, and an equation relating these two correlations is derived.