Temporal profile reshaping of high-intensity attosecond x-ray pulses by resonant propagation through dense gas

With ten orders of magnitude higher peak brightness than synchrotron radiation, XFELs offer opportunities to exploring x-ray nonlinear physics. Resonant propagation of ultra-intense attosecond x-ray pulses through dense gases creates nonlinear phenomena such as self-induced transparency and stimulated Raman scattering [1]. The strong interaction also induces temporal reshaping of the pulse.  We present simulations of resonant propagation of isolated high-intensity attosecond pulses from the Linac Coherent Light Source [2]. The attosecond pulses develop femtosecond oscillating tails (Burnham-Chiao ringing) and attosecond beats emerging from stimulated Raman scattering during propagation. We propose to measure these features by photoelectron streaking with circularly polarized light [2]. Attosecond pulse reshaping could be used for future FEL experiments or could be an issue when propagating pulses through resonant media.

[1] Kai Li, et al. Physical Review A  102, 053113 (2020).

[2] J. Duris, et al. Nature Photonics  14, 30-36 (2020).