Normalized single-shot X-ray absorption spectroscopy at a free-electron laser.

Area of Science:

• Atomic and Molecular Physics
• Materials Science
• Spectroscopy

Background:

• Dispersive X-ray absorption spectroscopy (XAS) is crucial for materials analysis.
• Existing XAS methods at free-electron lasers (FELs) can be limited by shot-to-shot intensity fluctuations.
• Accurate normalization is essential for reliable XAS data, especially for time-resolved studies.

Purpose of the Study:

• To implement and validate a novel reference scheme for dispersive XAS at a soft X-ray FEL.
• To enable high-precision, single-shot XAS measurements at FEL facilities.
• To achieve femtosecond time resolution in XAS experiments.

Main Methods:

• A transmission grating was utilized to split the FEL beam into signal and reference paths.
• Simultaneous spectral measurement of both beams allowed for shot-to-shot intensity normalization.
• The new scheme was tested at the FLASH FEL using a gadolinium oxide (Gd2O3) thin film sample.

Main Results:

• Excellent correlation (within a few percent) was demonstrated between the signal and reference beams at 143 eV.
• A Gd2O3 thin film absorption spectrum recorded using the new scheme showed excellent agreement with synchrotron data.
• The normalization scheme effectively compensated for FEL intensity variations.

Conclusions:

• The new reference scheme provides a robust method for single-shot XAS at FELs.
• This technique significantly enhances the reliability and precision of time-resolved XAS measurements.
• The developed method paves the way for advanced ultrafast material characterization at FELs.