Improvement of the hydrogenic model to give more accurate values of K-shell ionization cross sections

The hydrogenic (Coulomb-wavefunction) model is shown to yield K-shell ionization cross sections which are within a few percent of those given by Hartree-Slater calculations, provided an inner-shell screening constant of ≈0.6 is adopted rather than the customary value (≈0.3). This modification could result in more accurate quantification of very light elements (e.g. Li, Be, B) by electron energy-loss spectroscopy in a transmission electron microscope.