  Recently, a new device to measure the Orbital Angular Momentum (OAM)
electronic spectrum after elastic/inelastic scattering in a transmission
electron microscope has been introduced. We modified the theoretical framework
needed to describe conventional low loss electron energy loss spectroscopy
(EELS) experiments in transmission electron microscopes (TEM) to study surface
plasmons in metallic nanostructures, to allow for an OAM post selection and
devise new experiments for the analysis of these excitations in nanostructures.
We found that unprecedented information on the symmetries and on the chirality
of the plasmonic modes can be retrieved even with limited OAM and energy
resolutions.
