EELS is a very powerful technique as it allows for the measurement of energy state of the electrons after inelastic scattering. For this reason, it had incredible success in measuring atomic and chemical properties at the lowest scale. Often the energy information alone is sufficient to measure chemical species concentration, plasmon or even phonon excitations, especially with the recent improvements in energy resolution using high resolution spectrometers and source monochromators. However, it is sometimes desirable to add a second dispersion variable, to produce, for example, a momentum and energy double dispersion EELS or acquire a spectrum for a given momentum transfer.

But we can think of associating different quantities to the energy loss and most notably the Orbital Angular Momentum (OAM), the component of the angular momentum along the main electron propagation direction. Thanks to the new idea of miniaturized electron optics we developed the OAM sorter [1,2]: probably one of the most innovative electron optics elements now being developed now controlled by deep learining autoalignment procedure.

The advantage of a doubly dispersed OAM_EELS experiments is that some measurements becomes feasible or much easier if the OAM is chosen as projection state. Among these Electron Magnetic Circular Dichroism (EMCD) [3], multipolar transition, excitation of Plasmon with specific OAM, plasmonic dichroism.

The example of EMCD is particularly  relevant. In fact, while such a technique is quite cumbersome in the case of linear momentum (q, E) dispersed EELS and requires the measurement of the EELS signal interference, it results completely natural in the OAM basis [4] (ℓ, E) where the magnetism introduces an asymmetry between the ℓ = -1 and ℓ = +1 channels.

More in general Laurenco-Martins [5] demonstrated in different context that an dichroic +1/-1 OAM measurement is equivalent to a circularly polarized optical absorption measurement. Probing OAM is therefore also relevant in the case of plasmon modes excitation [6].

Another potential use of OAM sorter is to more easily single out specific character of multipolar transitions. For example we studied the transitions to σ, π states in 2D materials.

The talk will explore the theoretical possibilities, the properties of the new OAM sorter and the early results in doubly dispersive OAM-EELS experiments. We will conclude with a prospective also on different experiments made available by miniaturized optics.