Theory of Image Formation by Inelastically Scattered Electrons in the Electron Microscope

This chapter outlines a quantum-mechanical theory of image formation in the electron microscope, which considers both elastically and inelastically scattered electrons. It examines the properties of the mixed dynamic form factor and its interrelation with the generalized dielectric function including local field effects. The mixed dynamic form factor can be viewed as a generalization of the ordinary dynamic form factor. The intensity distribution in the image of two model objects has been calculated in the chapter. The calculation of the inelastic image necessitates knowledge of the local scattering and excitation properties of the object. The image of an atom formed by the inelastically scattered electrons (in dipole approximation) is much more blurred than that formed by the elastically scattered electrons. The calculations of images formed by dipole-surface-plasmon-loss electrons show that for low energy losses and high resolution the image of a sphere consists of a ring of high intensity about the projected surface.