Superweak momentum transfer near optical vortices

Near a vortex in a monochromatic light beam, the length of the local wavevector (phase gradient) can exceed the wavenumber in any of the plane waves in the superposition representing the beam. One way to detect these 'superweak' momenta could be by 'superkicks' imparted to a small particle located near the vortex, by absorbing individual large-momentum photons from the beam. A model for this process is a two-level atom with a transition resonant with the light beam. A semiclassical analysis shows that the momentum distribution of the atom is shifted by interaction with the vortex beam, by amounts that can almost reach the target superkicks and are usually greater than the momenta in the plane waves comprising the beam.