R-matrix with time-dependence calculations and benchmark experiments for three-sideband RABBITT in helium.

Further analyzing recent experimental results [1], we compare the predictions from several R-matrix with time-dependence (RMT) [2] calculations for a modified three-sideband version [3-5] of the ``reconstruction of attosecond beating by interference of two-photon transitions" (RABBITT) [6] configuration applied to helium. Increasing the number of coupled states in the close-coupling expansion used to describe the ejected-electron--residual-ion interaction generally does not change the results significantly. Overall, good agreement is achieved between the experimental data [1] and the theoretical predictions, with the remaining discrepancies likely being due to challenges in determining experimental parameters such as the peak intensity as well as the time dependence and the weight of the various frequency components in the pulse with high accuracy. Special attention, however, is needed for the threshold sideband, which is very sensitive to the coupling to the bound Rydberg states in the under-threshold (uRABBITT) setup [7]. Our latest results will be presented at the conference.

[1] D. Bharti et al., https://arxiv.org/abs/2309.10877 (2023), accepted for Phys. Rev. A 109 (2024).

[2] A. C. Brown et al., Comput. Phys. Comm. 250 (2020) 107062.

[3] A. Harth et al., Phys. Rev. A 99 (2019) 023410.

[4] D. Bharti et al., Phys. Rev. A 103 (2021) 022834.

[5] D. Bharti et al., Phys. Rev. A 107 (2023) 022801.

[6] P. Paul et al., Science 292 (2001) 1689.

[7] M. Swoboda et al., Phys. Rev. Lett. 104 (2010) 103003.