Probing photoionization dichroism of excited electron ring currents by chiral photoelectron spectroscopy

Electron ring currents in atoms carry the nonzero azimuthal quantum number that determines their rotation velocities. Here we tune the rotation velocity of electron ring currents by multiphoton excitation with strong ellipticity-controlled laser fields, and then we probe the ionization dynamics of the ring currents in continuum states and excited states with a chiral light field. We obtain photoionization dichroism of the angular-momentum-varied ring currents, and we find that the ring currents with high angular momenta are more easily ionized by a corotating circularly polarized light field, which is different from multiphoton or tunneling ionization of ground-state ring currents. The ab initio solution of the time-dependent Schr\"odinger equation and the classical dynamics simulation agree with our measurements. This study may have implications for the control of the rotation velocity of electron ring currents and the extraction of chiral dynamical information in strong-field ionization.