Progress in electron Compton scattering

Abstract

Use of electrons as a probe instead of photons for Compton scattering experiments has been suggested in 1981 by B.G. Williams et al. The advantages, compared to conventional Compton scattering, are evident: a cross section higher by five orders of magnitude, extraordinary spatial resolution, on-line specimen manipulation, and all the additional information that is available in an analytical electron microscope. With PEELS nowadays available, and with the solution of the background problem, electron Compton profiles (CPs) can now be studied. Directional electron CPs of Si could be obtained by use of a two-beam geometry. In the intermediate momentum region, theory fits our results better than the results from conventional γ-ray and X-ray experiments. Electron CPs of amorphous allotropes of carbon could be interpreted in terms of a charge transfer between s and p orbitals. In a crystal, the CP contains interference terms from scattering with different momentum transfer. They are caused by momentum correlation (off-diagonal elements of the momentum density in the reciprocal lattice), and can be described by the mixed dynamical form factor. In the two-beam case these terms are proportional to the excitation error. An experiment is suggested in order to obtain the off-diagonal elements of the momentum density.