Practical Electron Microscopy and Database

Information limit depends on the damping envelope incorporating partial temporal coherence due to chromatic aberration, but not partial spatial coherence due to beam convergence.

Assuming the electron beam is a Gaussian-shaped source, a high-frequency damping function on TEM images can be approximately given by,

          -------------------- [4155]
where,
         Δ -- The defocus spread due to a nonmonochromatic beam and electronic instabilities,
         λ -- The wavelength of the electron beam,
         k -- Spatial frequency,
         θ_c -- The beam convergence angle,
         Δf -- The defocus,          
         C_s -- Spherical aberration of the objective lens.