Liquid X-ray scattering with a pink-spectrum undulator

Area of Science:

• Condensed matter physics
• Materials science
• X-ray science

Background:

• Synchrotron X-ray sources utilize undulators to generate quasi-monochromatic 'pink' beams.
• Pink beams possess a characteristic saw-tooth spectrum with bandwidths ranging from 1% to 15%.

Purpose of the Study:

• To investigate X-ray scattering from liquids using pink undulator beams.
• To analyze the impact of spectral bandwidth on scattering data (S(q)) and real-space (r-resolved) signals.

Main Methods:

• Examined X-ray scattering as a function of spectral bandwidth.
• Described the undulator spectrum using a single exponential with a low-energy tail.
• Applied a sin-Fourier transform and Warren convergence factor for r-resolved signal analysis.

Main Results:

• Pink beams provide a 250-500 fold intensity gain, vital for time-resolved studies.
• Spectral bandwidth causes slight shifts and dampening of features in S(q) compared to monochromatic data.
• The low-energy tail of the pink spectrum shifts features to higher angles and reduces amplitude slightly.

Conclusions:

• Pink beams are highly advantageous for time-resolved X-ray scattering due to intensity gains.
• Deformation in r-resolved signals from pink beams is minimal compared to artifacts from finite data ranges.
• Q-resolved and r-resolved signals exhibit distinct behaviors when using pink X-ray spectra.