A new approach to study bonding anisotropy with EELS

A novel method to study the anisotropy of electron scattering is presented. The technique makes use of the two-dimensional capabilities of energy filters in transmission electron microscopes to study the energy-filtered scattering patterns obtained at different energy losses near ionization edges. The technique is demonstrated for the C-K edge in pyrolific graphite at energy losses corresponding to the continuum background prior to the C-K edge, the unoccupied pi* and sigma* transitions and the continuum after the near-edge fine structure. The distribution of scattering for transitions to unoccupied pi* and sigma* electronic states is remarkably different as expected from experiments using the conventional techniques. The fine structure of the scattering distribution demonstrated with this approach, however reveals additional details that can be explained by the broader angular extent of the sigma-orbitals between carbon atoms. Good agreement between the one-dimensional profiles extracted from the two-dimensional data and scattering models is observed. (c) 2004 Elsevier B.V. All rights reserved.