XUV pump-XUV probe transient absorption spectroscopy at FELs

Area of Science:

• Atomic, Molecular, and Chemical Physics
• Ultrafast Spectroscopy
• Free-Electron Laser Science

Background:

• Ultra-intense extreme-ultraviolet (XUV) and X-ray free-electron lasers (FELs) enable advanced spectroscopic methods.
• Non-linear spectroscopy in the XUV and X-ray range is crucial for understanding ultrafast dynamics.
• Existing techniques often lack the required resolution or spectral range for complex systems.

Purpose of the Study:

• To demonstrate an experimental setup for all-XUV transient absorption spectroscopy for gas-phase targets.
• To achieve high spectral resolving power (E/ΔE ≈ 1500) and sub-femtosecond interferometric resolution.
• To enable the study of non-linear light-matter interactions and ultrafast molecular dynamics.

Main Methods:

• Utilized an experimental setup at a free-electron laser (FEL) facility.
• Employed an all-XUV transient absorption spectroscopy technique.
• Achieved broad XUV photon energy coverage (20–110 eV) with single-shot detection capability.

Main Results:

• Successfully demonstrated intensity- and time-resolved non-linear XUV-FEL light-matter interactions in neon.
• Observed non-resonant ionization and resonant coupling dynamics, including XUV-induced Stark shifts.
• Tracked XUV-initiated dissociation dynamics of oxygen and diiodomethane with site-specific resolution.

Conclusions:

• The developed setup enables advanced non-linear spectroscopy in the XUV spectral range.
• The method provides single-shot phase-locked XUV pulse pairs for future experiments.
• This work lays the foundation for coherent non-linear spectroscopy in the XUV and X-ray regimes.