L-subshell fluorescence yields and Coster-Kronig transition probabilities with a reliable uncertainty budget for selected high- and medium-Zelements

Abstract

Photon-in/photon-out experiments at thin specimens have been carried out to determine L-subshell fluorescence yields as well as Coster-Kronig transition probabilities of Au, Pb, Mo, and Pd using radiometrically calibrated instrumentation in the Physikalisch-Technische Bundesanstalt (PTB) laboratory at the electron storage ring BESSY II in Berlin. An advanced approach was developed in order to derive the fluorescence line intensities by means of line sets of each subshell that were corrected for self-absorption and broadened with experimentally determined detector response functions. The respective photoelectric cross sections for each subshell were determined by means of transmission measurements of the same samples without any change in the experimental operating condition. All values derived were compared to those of earlier works. A completely traceable uncertainty budget is provided for the determined values.The complete understanding of atomic excitation and emission processes as well as the exact knowledge of related cross sections are crucial for quantitative investigations of elemental concentrations in unknown specimens by x-ray spectrometry. The emitted spectral response of an unknown sample following the excitation by x rays is based on both the specimen's elemental composition and the related atomic processes, the probability of which depends on a set of atomic fundamental parameters. For the quantitative determination of the respective elemental concentrations, the cross sections for photoionization of the (sub)shell and for both elastic and inelastic scattering, the related fluorescence yield, and transition probabilities associated with the specific inner-shell excitations have to be exactly known. Therefore, the uncertainty of these fundamental parameters is relevant for reference-based as well as reference-free x-ray fluorescence analysis results. Here, a reliable uncertainty budget is needed [1-3].Krause et al.[4] estimated relative uncertainties by comparing of theoretical total photoionization cross sections with those determined experimentally, which have still mostly remained valid since the late 1970's [5]. In addition, one may assume that most of the relative uncertainties are estimated rather from the compilation of available data than from the individual experimental uncertainty budget. An example of a compilation-based uncertainty indication is the compilation of theoretical data by Puri et al. published in 1993 for elements 25 Z 96 based on the relativistic Dirac-Hartree-Slater model [6], which states only a fitting error of 2% for elements with higher Z.The fluorescence yields as well as Coster-Kronig (CK) transition probabilities were investigated in earlier works, e.g., by electron-induced high-resolution x-ray fluorescence spectroscopy, Kα-Lα-coincidence methods [7]. When monochromatic tunable synchrotron radiation became available, photoionization experiments were also carried out, but the respective relative uncertainties could not be reduced significantly [5]. This was partially...

Theoretical and experimental determination of K - and L -shell x-ray relaxation parameters in Ni

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Experimental determination of the x-ray atomic fundamental parameters of nickel

“…Besides these investigations, the transmission data for the photon energies of the fluorescence lines as well as for the excitation energies which were already determined for the mass attenuation coefficients were used to determine the attenuation correction factors experimentally. Thus the attenuation corrections are independent of data bases for the mass attenuation coefficient [24]. By applying Equations 5 and 6, the fluorescence production yield of each subshell can be determined, …”

Reference-free, depth-dependent characterization of nanolayers and gradient systems with advanced grazing incidence X-ray fluorescence analysis

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