Secondary fluorescence correction formulae for X-ray microanalysis — I Parallel-sided thin foil, wedge, and bulk specimens

Secondary fluorescence correction formulae have been derived for specimen geometries that are commonly employed in the analytical electron microscope. Formulae have been derived for parallel-sided thin foil and bulk (electron probe microanalysis) specimens, for which established correction formulae currently exist, and for wedge-shaped specimens, for which no formulae have been available to date. All derivations explicitly account for the absorption of fluoresced X-rays leaving the specimen en route to the spectrometer, which the existing correction formulae neglected wholly or in part. It is shown that the existing secondary fluorescence correction formula of Nockolds et al. for parallel-sided thin foils, which entirely neglects the absorption of secondary X-rays, is sufficiently accurate as long as the “sec α” factor is omitted. An additional factor (y(x + y) in Reedʹs notation) should be appended to the existing secondary fluorescence correction formula for bulk specimens in the electron probe microanalyzer to account for near-surface absorption of fluoresced X-rays, which was neglected by Castaing. The difference in the secondary fluorescence corrections calculated with the Φ(ϱz) dependencies of Lenard (exponential) and Packwood and Brown (modified Gaussian) is shown to be negligible.