Imaging ring-current wave packets in the helium atom

Venzke, J.; Becker, A.; Jaron-Becker, A.

doi:10.1103/physreva.103.042808

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Imaging ring-current wave packets in the helium atom

Venzke, J.·Becker, A.·Jaron-Becker, A.

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Abstract

We study the reconstruction of a wave packet and the corresponding electron dynamics in an atom via photoelectron angular distributions (PADs) in a pump-probe scheme as a function of time delay. The method is applied to the superposition of ground and one or two excited states in helium atom representing field-free charge migrations on the attosecond timescale in form of ring currents around the core. It is based on the interference between one- and two-photon transitions from ground and excited states into the continuum. In the reconstruction predictions of first- and second-order perturbation theory are used to determine the unknown phases and amplitudes from the PADs, which we simulate via solutions of the time-dependent Schrödinger equation in single-active-electron approximation. Results of calculations show that the reconstruction technique works well for peak laser intensities less than 10 13 W/cm 2 . Knowledge of the electric field of the probe pulse is required with shot-to-shot variations of carrier-to-envelope phase and peak intensity of up to 10% and 20%, respectively. The relevance of different one- and two-photon pathways for the reconstruction as a function of peak intensity and pulse duration is analyzed—specifically their role for ultrashort probe pulses with broad bandwidths.

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74 ATOMIC AND MOLECULAR PHYSICS Atomic & molecular processes in external fields Optics Photoemission Physics Single- and few-photon ionization & excitation Ultrafast phenomena

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Venzke, J., Becker, A., Jaron-Becker, A.. 2021-04-05. Imaging ring-current wave packets in the helium atom. https://doi.org/10.1103/physreva.103.042808

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