Efficient transient X-ray absorption spectroscopy

Delay vs. photon energy map of an ammonium iron(III) oxalate solution. The large bandwidth emission covers the full XANES range, making time-consuming monochromator scans obsolete.

By combining the unique large bandwidth emission mode of SwissFEL’s ARAMIS undulator and diffractive X-ray optics made of diamond, we have demonstrated a new method for time-resolved X-ray absorption near edge structure (XANES) spectroscopy that enables faster data acquisition and requires smaller sample quantities for high-quality data. A beam-splitting grating configuration provides simultaneous measurements of the spectra of the incoming XFEL pulses and transmitted signal through a sample, which is crucial to normalize the intrinsic spectral fluctuations of the self-amplified spontaneous emission operation. In a team effort of  several PSI groups and collaborators from the European XFEL, the method was applied to measure the absorption spectra of liquid solution of ammonium iron(III) oxalate solution at the ALVRA end station of SwissFEL. With the new experimental scheme it was possible to measure the response of the XANES signal to a UV pump laser pulse within a few hours. 

Small Methods 2024, 2301328, DOI: 10.1002/smtd.202301328