Symmetry-selected electron-energy-loss scattering in diamond

Inelastic electron scattering using a two-beam channeling condition is used for the first time to create excitations having selectable even or odd symmetry relative to an atom column. The method is first established using plasmon and interband scattering in diamond. Next, for the carbon 1s absorption edge, scattering to modes having odd symmetry gives a strong exciton peak. Scattering to modes having even symmetry results in a depressed edge having no exciton peak in evidence. © 1993 The American Physical Society.