Optimization of parameters in electron probe microanalysis

Abstract

A method for the refinement of atomic and experimental parameters applicable to several spectroscopic techniques is presented. This kind of procedure, previously used in x‐ray diffraction, is shown to be a powerful tool in electron probe microanalysis (EPMA). This method consists of minimizing the differences between an experimental x‐ray spectrum and a function proposed to account for the bremsstrahlung and characteristic peaks from the corresponding sample, and also for detection artifacts. This complicated function involves several parameters related to different sources (x‐ray production, x‐ray attenuation, sample composition, x‐ray detection, etc.). Initial values must be supplied for them, and after a numerical iterative procedure is performed, improved values are achieved. Depending on the particular situation, certain parameters may be known a priori, so that they can be fixed, allowing the others to vary. In this way, the method can be used for different purposes: determination of atomic parameters such as fluorescence yields, transition rates or photoelectric cross‐sections, quantitative standardless analysis, determination of detector characteristics, etc. This work is intended to present the general aspects of the method for refining EPMA parameters, and to give some examples of its application to the aforementioned issues. Even when only EPMA spectra are included in this work, the method can be applied to different spectroscopic techniques, such as x‐ray fluorescence, particle‐induced x‐ray emission, etc. Copyright © 2001 John Wiley & Sons, Ltd.

Layered structure of friction films revealed by the comparison between multi-energy X-ray microanalysis and Monte Carlo simulations

“…Further studies are being developed to determine the structure and composition of the friction film using analytical functions [28] and Monte Carlo simulations.…”

Fast and accurate expression for the Voigt function. Application to the determination of uranium M linewidths

“…3 along with the fit performed by means of the POEMA program [17]. As can be seen, the agreement is very good in the whole energy range studied.…”

“…Besides that, a good fitting method that take into account most of the fundamental and experimental processes in a realistic manner is necessary. In this sense, a parameter refinement method involving Voigt profiles for the description of the characteristic peaks, like the one implemented in the POEMA program [17], shows a good performance in this application.…”

“…The Voigt function was implemented in the software POEMA developed for electron probe microanalysis (EPMA) for the optimization of atomic and experimental parameters [17]. With this purpose, Eq.…”

The prediction of thick target electron bremsstrahlung spectra in the 0.25–50 keV energy range

“…The description of this photon distribution has drawn the attention of different research areas, since the adequate knowledge of the emitted spectrum may be used for different purposes: X-ray tube spectrum input for quantitative X-Ray Fluorescence or related techniques, background subtraction in x-ray spectra induced by electron impact [37], standardless quantitative electron probe microanalysis (EPMA) for particles [38] or bulk samples [39], etc.…”