Characteristic X‐ray production cross‐sections for standardless elemental analysis in EDX

SUMMARY Measurements have been made of cross‐sections for the production of X‐rays following ionization of the K‐shell by fast electrons for a range of elements and incident electron energies. These data have been fitted to a simple functional expression for the ionization cross‐section. This model, the Bethe model, includes two empirical fitting parameters. We found that a single universal pair of parameters may be used to allow the model to predict cross‐sections with a mean error of ∼ 7% and a maximum error of ∼ 20% over the range of conditions considered. A relativistic form of the Bethe model yields a small improvement in accuracy for higher incident electron energies. Measurements have also been made of L‐shell production cross‐sections. It is expected that the Bethe model will apply also to the L‐shell. Comparison of experimental and calculated K/L‐shell cross‐section ratios generally supports this, but uncertainties in the values in the literature for L‐shell fluorescence yields precludes the drawing of any firm conclusions here.