Practical Electron Microscopy and Database

In general, the higher the effective atomic number, the higher is the inelastic differential cross-section. However, the ratio of the inelastic to the elastic scattering cross-section is inversely proportional to the effective atomic number, [1]
          ------------------------ [947]
where,          
         σ_i -- the inelastic scattering cross-section,
         σ_e -- the elastic scattering cross-section,
         Z_eff -- the effective atomic number,
         C -- a coefficient,
          -- the characteristic angle corresponding to the mean energy loss.

Figure 4755b shows the angle at which inelastic and elastic differential cross-sections are equal, as a function of the atomic number Z at the energy loss of 10 eV.

[1] A.V. Crewe, J.P. Langmore, M.S. Isaacson, Physical aspects of electron microscopy and microbeam analysis, in: B.M. Siegel, D.R. Beaman (Eds.), Wiley, New York, 1975, p. 47.
[2] Lin Gu, Wilfried Sigle, Christoph T. Koch, Jaysen Nelayah, Vesna Srot, Peter A. van Aken, Mapping of valence energy losses via energy-filtered annular dark-field scanning transmission electron microscopy, Ultramicroscopy 109 (2009) 1164–1170.