The quantum processes involved in the interaction of matter with, separately,an electron vortex(EV) and an optical vortex (OV) are described, with mattermodelled in terms of a neutral two particle atomic system, allowing for boththe internal (electronic-type) motion and the gross (center of mass-type)motion of matter to be taken into account. The coupling of the atomic system tothe EV is dominated by Coulomb forces, while that of the OV is taken in the$\mathbf{p}\cdot\mathbf{A}$ canonical form which couples $\mathbf{A}$, thetransverse vector potential of the optical vortex, to the linear momenta of thetwo-particle system. An analysis of the dipole active transition matrix elementis carried out in each case. The electron vortex is found to be capable ofexchanging its orbital angular momentum (OAM) with both the electronic and thecenter of mass motions of the atomic system in an electric dipole transition.In contrast, for electric dipole transitions the optical vortex is found to becapable of exchanging OAM only with the center of mass. The predictions arediscussed with reference to recent experiments on electron energy lossspectroscopy (EELS) using EVs traversing magnetised iron thin film samples andthose involving OVs interacting with chiral molecules.
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