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SUMMARY Scattering cross‐sections for the interpretation of the scattering‐absorption contrast of microscopical images of amorphous biological specimens are calculated. The constituent atoms are treated as independent particles and their atomic potential is approximated by a modified Lenz‐Wentzel potential. Both elastic and inelastic scattering processes are considered. Formulas of the effective elastic and inelastic atom scattering cross‐sections are derived for both a CTEM with hollow‐cone illumination and a STEM using an annular detector. The scattering‐absorption contrast is plotted as a function of the atomic number for a CTEM applying parallel illumination and a STEM using a dark‐field detector with maximum collection efficiency. The presented results are valid for acceleration voltages U in the range 20 kV< U <150 kV. Employing these data the ‘angular mass thicknesses’ of representative constituents of biological materials are determined. The application of the listed data is demonstrated by means of a special example.
Eusemann et al. (Wed,) studied this question.