Evaluation of the energy-dispersive x-ray spectra of high-Z elements using Gaussian and Voigt peak shape profiles

The AXIL computer program, aimed at x-ray spectral deconvolution, was extended in order to take into account the broadening of peaks of K-series radiation of high-Z elements (Z > 50) due to the increasing contribution of the natural linewidth to the peak width. This effect needs to be taken into account in energy-dispersive spectrometry of K-series radiation of heavy elements, such as W, Au, Pb and U. The so-called Voigt peak profile function was implemented into the AXIL computer code. Based on the published literature data, a library of natural atomic level widths was created, containing the data for K, L1, L2, L3 atomic level widths of elements up to Z = 94. The database was necessary to calculate the Voigt peak profiles. The AXIL program user interface and the fitting procedures were adapted, allowing us to perform spectral evaluation using either Gaussian or Voigt peak profiles. The relevance of fitting the x-ray spectra of K-series radiation of high-Z elements with the Voigt peak shape model versus Gaussian peak approximation was thoroughly examined with the aid of simulated and measured spectra. The experimental x-ray spectra were measured using a high-voltage x-ray tube spectrometer utilizing a 130 kV/65 W tungsten anode x-ray tube and an ultra-low energy germanium detector. The results obtained showed that when using the Gaussian peak model the calculated peak areas and fitted peak widths are systematically biased. It was found that the value of the systematic error is a linear function of the ratio of the natural linewidth to the spectrometer energy resolution at the peak position. Copyright © 2001 John Wiley & Sons, Ltd.