Simulation of the electron dynamics of chiral systems in CEP-stabilized, intense laser fields
Final Report Abstract
The strong-field-driven ionization dynamics of larger, non-diatomic molecules still constitutes a major challenge for a theoretical and numerical description. We have designed and implemented a model system allowing us to describe the strong-field dynamics fully based on ab initio quantum dynamics. At the same time, we have developed a methodology to describe these dynamics based on classical trajectories and, to a certain level, based on the strong-field approximation, which is commonly applied to describe such processes. The combination of these very different methods constitutes a powerful toolbox enabling us to analyze the complex pattern of the photoelectron momentum distribution. This way, we were able to disentangle the contributions of excited states and the long-range character of the potential. Upon interaction with circularly polarized laser fields, the long-range character merely induces a small shift in the spectra, while the contribution of excited states is in several cases essential. In particular in near-infrared laser fields, compared to mid-infrared drivers, and for systems with larger internuclear distances, when excited electronic states are energetically closer, the contribution of excited states strongly affects the photoionization dynamics and the resulting electron spectra. We have performed these calculations starting from planar, non-colinear triatomic model systems, allowing us to disentangle the contributions and gain a deeper physical picture, and extended these investigations to nonplanar model systems consisting of four atoms, featuring possibly an asymmetric potential landscape, thus mimicking chiral systems. This allowed us to investigate the fundamental processes leading to strong-field photoelectron circular dichroism (PECD). We found that this strong-field PECD is more pronounced, when the ionization can be described to proceed predominantly in the multiphoton regime – when electronic excited states are involved – and almost vanishes for mid-infrared driving wavelengths and ionization proceeding more via tunneling – relying mainly on electronic ground state contributions. Also, we have investigated the influence of molecular averaging as well as the impact of the carrier-envelope phase on the strong-field PECD. Finally, we have started to investigate real molecules and the strong-field ionization dynamics with the help of real-time real-space time-dependent density functional theory, in close collaboration with the experiment.
Publications
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„Strong-field ionization of asymmetric triatomic model molecules by few-cycle circularly polarized laser pulses”, J. Mod. Optics, 2017, 64, 1104 – 1111
M. Paul, L. Yue, S. Gräfe
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„Imprints of the molecular electronic structure in the photoelectron spectra of strong-field ionized asymmetric triatomic model molecules “, Phys. Rev. Lett. 2018, 120, 233202-1 – 233202-5
M. Paul, L. Yue, S. Gräfe
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“Strong-field ionization dynamics of asymmetric equilateral triatomic model molecules in circularly polarized laser fields”, Phys. Rev. A 2019, 99, 053414-1 – 053414-22
M. Paul, S. Gräfe
