Wätzel J., and Berakdar J.

Photoionization from energetically distinct electronic states may have a relative time delay of tens of attoseconds. Here we demonstrate that pulses of optical vortices allow the measurement of such attosecond delays from magnetic sublevels, even from a spherically symmetric target. The difference in the time delay is substantial and exhibits a strong angular dependence. Furthermore, we find an atomic scale variation in the time delays depending on the target orbital position in the laser spot. The findings thus offer a method for spatiotemporal sensing of the magnetic states from which photoelectrons originate, with a spatial resolution far below the diffraction limit of the vortex beam. Our conclusions follow from analytical considerations based on symmetry, complemented and confirmed by full numerical simulations of the quantum dynamics.

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