Direct measurement of the PSF for Coulomb delocalization – a reconsideration

Highlight• Coulomb delocalization represents the radial extent of forces between a primary electron and atomic electrons within a thin specimen. • It also represents the specimen region over which information about the specimen is integrated, and the region over which energy is initially deposited. • It does not represent the region over which inelastic scattering takes place, or the region from which scattered electrons appear to originate. • The Coulomb point spread function cannot be measured as a broadening of the inelastic image of a small probe. An interpretation of Coulomb delocalization, which limits the spatial resolution of inelastic TEM or STEM images, is given. We conclude that the corresponding point spread function cannot be measured as a broadening of a STEM probe.