Abstract

The experimental determination of x-ray-production cross sections by electron impact on thick samples is faced in this work, especially focusing on the L subshells of Ag. The integrodifferential method used by An et al. is compared with a recently implemented approach involving the ionization distribution function. The first method has shown good results under suitable conditions, namely, when multiple scattering, bremsstrahlung enhancement, and other secondary effects are negligible. Monte Carlo simulations were performed in order to analyze the influence of these conditions and therefore to extend the validity range of the method by adding a correction factor. The second approach uses the ionization distribution function phi (rho z) to predict the intensity of the emitted photons; this magnitude is assessed by the POEMA software, previously developed, and it is used to determine correction factors to the cross sections included in the software database. Both approaches were tested by fitting several L-shell spectra measured in a wide interval of incident electron energies, ranging from 4.0 to 25 keV, with an electron microprobe equipped with a wavelength-dispersive spectrometer. The x-ray-production cross sections obtained for each L subshell and the total L x-ray-production cross section were compared with theoretical predictions based on the distorted-wave approach theory and with experimental determinations when available.