Disentangling intracycle interferences in the photoelectron spectrum of argon using orthogonally polarized, two-colour laser pulses

In recent years, the widespread availability of multi-dimensional photoelectron spectroscopy has created the opportunity to systematically study the complex interference patterns inherent to multiphoton ionization of atoms and molecules. The dominant interference mechanism in multiphoton ionization leads to discrete peaks in the photoelectron spectrum (PES) that are spaced by the photon energy of the driving laser field. This mechanism is called above-threshold ionization (ATI) and has its origin in the coherence of ionization events repeating at every oscillation of the optical field [1]. However, many more interference mechanisms contribute to the observed photoelectron spectrum. Specifically, photoelectrons emitted within one cycle of the optical field can also interfere on the detector. These interferences from photoelectrons originating in adjacent quarter-cycles of the optical field are also known as the temporal double slit (e.g., [1]). In addition, scattering of the photoelectron on the parent ion potential will give rise to holographic interferences [2], and laser induced electron diffraction [3].