Mechanisms of contrast and image formation of biological specimens in the transmission electron microscope

Abstract

SUMMARY A systematic account is given, in relation to amorphous and paracrystalline (especially biological) material, of electron scattering and image formation for the range of electron energy from 50 to 100 keV. Contrast mechanisms in both elastic and inelastic scattering are discussed and image formation is considered under both scattering contrast and phase contrast conditions.

Determination of the mass thickness of biological sections from electron micrographs

“…The mass scattering cross-section ST for scattering into all angles is related to the mean free path A T for electron scattering by ST^= AT (Burge & Smith, 1962). Evidently u(01) will depend on the scattering model used and the average atomic number of the specimen (Burge, 1973). However, the results for ST given in Table 1 show that S T~ is virtually independent of Z so that at least (1) is not very dependent on the specimen.…”

“…(a) is obtained by calculating the angular distribution of the transmitted electrons, including both elastic and inelastic scattering (Burge, 1973), followed by an integration over the semi-angle of the objective aperture. Thus .…”

Imaging with Electrons, X-rays, and Microwaves

“…In dark-field conditions (e.g., Frank, 1972), a quadratic relationship exists that is not readily conducive to optical processing. Bright-field conditions imply minimal electron beam damage (e.g., Burge, 1973). The functional part of this chapter concerns the requirements for and method of implementation of a practical method of image improvement (i.e., deblurring) by the application (see Burge & Scott, 1975a-d) to electron microscopy of Lohmann-type computer-plotted binary holograms.…”

“…However, the low-resolution image must be interpreted bearing in mind the extent of the spatial coherence of the incident electron beam. For the conventional thermal electron microscope source the extent of partial spatial coherence is limited to a few atomic diameters, for coarser structure than this, the distinction between elastic and inelastic scattering contrast mechanisms is not worth preserving, as in the method of quantitative mass-thickness electron microscopy (see Burge, 1973). o0015 (c) It is essential to account for both the high-resolution phase and highresolution amplitude components of an image where discrete heavy atoms or heavy atom complexes exist in the presence of light atoms.…”

An automated procedure for the correction of background due to inelastic scattering in electron diffraction patterns

“…la). The intensity is greatest in the forward direction and decreases rapidly with scattering angle (see, for example, Burge, 1973). Because of the rapid decrease with scattering angle, reflexions are displaced from their true positions and methods of background correction based on local estimates (Langridge, Wilson, Hooper, Wilkins & Hamilton, 1960) are subject to considerable error.…”