Average <sub>a</sub>(<em>E</em><sub>X</sub>)-values of elements and oxides and percentage differences calculated using the XCOM and FFAST attenuation coefficients; uncertainties, seen in italics, apply to the rightmost decimal place of the data <strong>Abstract</strong> Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1–2 keV) for light elements

2013-09-06T00:00:00Z (GMT) by C M Heirwegh I Pradler J L Campbell
<p><b>Table 3.</b> Average <sub>a</sub>(<em>E</em><sub>X</sub>)-values of elements and oxides and percentage differences calculated using the XCOM and FFAST attenuation coefficients; uncertainties, seen in italics, apply to the rightmost decimal place of the data</p> <p><strong>Abstract</strong></p> <p>Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1–2 keV) for light elements. Characteristic x-ray yields generated in thick samples of Mg, Al and Si in elemental and oxide form, were compared to fundamental parameters computations of the expected x-ray yields; the database for this computation included XCOM attenuation coefficients. The resultant PIXE instrumental efficiency constant was found to differ by 4–6% between each element and its oxide. This discrepancy was traced to use of the XCOM Hartree–Slater photo-electric cross-sections. Substitution of the FFAST Hartree–Slater cross-sections reduced the effect. This suggests that for 1–2 keV x-rays in light element absorbers, the FFAST predictions of the photo-electric cross-sections are more accurate than the XCOM values.</p>