Valence excitations in electron microscopy: resolved and unresolved issues.
Recent progress in the interpretation of spatially localized valence loss spectra is outlined. For a well-defined geometry of dielectric interfaces, detailed and quantitative analysis is now possible. In other cases, useful results may still be available although the common assumption that the spectrum at each point should be directly related to that from a uniform reference sample of appropriate composition may not always be valid.
Howie
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Cavendish Laboratory, University of Cambridge, Madingley Road, CB3 0HE Cambridge, UK. ah30@phy.cam.ac.uk