@article{12558,
  author = {J. Venzke and Andreas Becker and Agnieszka Jaron-Becker},
  title = {Imaging ring-current wave packets in the helium atom},
  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 Schrodinger 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.},
  year = {2021},
  journal = {Physical Review A},
  volume = {103},
  month = {2021-04},
  publisher = {American Physical Society (APS)},
  issn = {2469-9926, 2469-9934},
  doi = {10.1103/physreva.103.042808},
}