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 C M Heirwegh I Pradler J L Campbell 10.6084/m9.figshare.1012794.v1 https://iop.figshare.com/articles/dataset/_Average_img_src_http_ej_iop_org_icons_Entities_epsi_gif_alt_epsilon_align_baseline_sub_a_sub_em_E_e/1012794 <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> 2013-09-06 00:00:00 percentage differences FFAST attenuation coefficients FFAST predictions Hartree Technology XCOM oxide form XCOM values light elements XCOM attenuation coefficients rightmost decimal place parameters computations light element absorbers kev pixe National Institute yield Atomic Physics Molecular Physics