Abstract
The enormous advances in the generation of advanced light sources have enabled the exploration of the
ultrafast dynamics in atoms and molecules, thereby promising a rich field of possibilities in the control of
matter. One aim of quantum coherent control is to steer electronic motion in atoms and molecules in
specific directions or locations. This might be achieved by introducing a controlled delay between two or
more pulses. Other applications of such delays are RABBITT (Reconstruction of Attosecond Beating By
Interference of Two-photon Transitions) setups, which have also been extended to more than two photons.
We discuss a variety of schemes by which control of the PAD asymmetry can be achieved, such as
interfering one-photon and two-photon ionization pathways in a region of an intermediate resonance,
overlapping the XUV pulse with an infrared (IR) field as in RABBITT, or using circularly polarized light.
Employing circularly polarized light opens up a number of particularly interesting possibilities in the study
of multi-photon ionization processes, such as the investigation of circular dichroism when two fields can
either be co-rotating or counter-rotating.