Nondipole laser-assisted photoinonization: the streaking regime

When atoms and molecules are exposed to an extreme ultraviolet (XUV) pulse and infrared (IR) laser field that overlap in space and time, the so-called laser-assisted photoionization emission (LAPE) processes take place. Depending on whether the XUV pulse duration is shorter, or longer, than one IR optical cycle (T = 2π/ωIR, where ωIR is the frequency of the IR laser), two different scenarios arise: the sideband or the streaking regime respectively. The photoelecton momentum distribution (PMD) can be recorded for different delays between the pulses, so the photoionization dynamics becomes accessible with attosecond resolution.

In recent years, there has been increasing interest in exploring strong laser–matter in-
teractions beyond the widely used electric dipole approximation [1]. However, the streaking scenario remains unexplored. In this work, we introduce a theoretical model to describe the streaking regime within the strong field approximation including first-order nondipole corrections [2, 3]. In order to study a specific case, we have focused on XUV ionization of a 1s-state hydrogen atom assisted by a ellipctically polarized IR laser.

We will systematically explore the PMD for different delays and making use of the semiclassical model (SCM) to gain an overall understanding of PMD structures, we will analyze the PMD as in the attoclock process [4].

[1] J Maurer and U Keller 2021 J. Phys. B 54 094001
[2] C J Joachain, N J Kylstra, and R M Potvliege 2012 Atoms in Intense Laser Fields, Cambridge University Press.
[3] R Della Picca et al. 2023 Phys. Rev. A 107 053104
[4] R Della Picca et al. 2025 Phys. Rev. A 112 023111