Non-linearity correction of the velocity scale of a Mössbauer spectrum

Abstract

The calibration of the velocity scale of a Mössbauer spectrum using a standard absorber is approximated by a non-linear velocity-to-channel function. In case of triangular or sinusoidal mode, the full (i.e., unfolded) spectrum is evaluated. The non-linear correction by a Fourier expansion up to 18 coefficients allows for fitting calibration spectra of α-iron of an effect-to-noise ratio of ≈103 with χ2-values of unity within the standard deviation of χ2. The fit of the spectrum of 57Co/α-Fe source versus α-Fe absorber did not identify any broadening of the emission and absorption lines beyond the natural linewidth. The described procedure provides an efficient check of the linearity of the drive unit and its dependence on conditions like load, frequency, maximum velocity or temperature so that, by this way, its ageing can be monitored.