The Attoclock in Laser-Assisted Atomic Photoionization

Measuring the timing of photoionization requires understanding how light-driven electron motion is encoded in the detected electron distribution. In this work, we present a theoretical study of a laser-assisted attoclock, in which a short extreme-ultraviolet pulse releases electrons from an atom and a rotating infrared field maps their emission timing onto their final directions of motion. By orienting the polarization of the ionizing pulse perpendicular to the plane of rotation of the infrared field, we extend this approach to stronger infrared fields and simplify the interpretation of the electron distribution. We identify pulse conditions that produce a clear angular timing map and explain the directions of strongest emission using a semiclassical description. We then show how an energy-dependent phase of the ionization amplitude changes both the position and orientation of the resulting ring-shaped momentum distribution. Comparisons between theoretical descriptions assess the influence of the attraction between the outgoing electron and the residual ion. Finally, we demonstrate how a temporal shift can be extracted by accounting for both the displacement of the ring and the location of its strongest emission. This work provides a basis for interpreting angular shifts in laser-assisted photoionization and for developing attosecond timing measurements.