A simple new method to obtain high angular resolution ω–q patterns

A simple new method is described to obtain angle-resolved energy loss spectra, or `ω–q patternsʹ, with high angular resolution. The specimen is raised from its normal position so that diffracted images of the convergent probe (a `diffraction patternʹ) are seen in the image plane. The angular resolution of this pattern depends on the probe size and specimen defocus but can be as high as 2 μrad making the new method extremely useful for studying features with small q in angle-resolved energy loss spectra. Using a narrow slit at the entrance aperture to a Gatan imaging filter it is possible to form ω–q patterns with very high angular resolution. Spectra from aluminium and diamond are used as examples to show the potential worth of this new method.