Capturing EELS in the reciprocal space
In this work two aspects of momentum-dependent electron energy loss spectrometry are studied, both in the core-loss and in the low-loss region. In the case of core losses, we focus on the demonstration and the interpretation of an unexpected non-Lorentzian behavior in the angular part of the double-differential scattering cross-section. The silicon L-3 edge is taken as an example. Using calculations we show that the non-Lorentzian behavior is due to a change in the wavefunction overlap between the initial and the final states. In the case of low losses, we first analyze the momentum-dependent loss functions of coinage metals Cu, Ag, and Au. We then demonstrate how advanced electronic structure calculations can be used to build simple models for the dielectric function that can then serve as a basis for the calculation of more complicated sample geometries.