Towards ultrafast dynamics with split-pulse X-ray photon correlation spectroscopy at free electron laser sources

Area of Science:

• Condensed matter physics
• Materials science
• Ultrafast spectroscopy

Background:

• Understanding atomic-scale fluctuations is crucial for materials science.
• Current methods face challenges in probing ultrafast dynamics.

Purpose of the Study:

• To develop and demonstrate a split-and-delay system for ultrafast X-ray photon correlation spectroscopy.
• To enable the study of dynamic processes in equilibrium and non-equilibrium materials.

Main Methods:

• Utilized a perfect crystal based split-and-delay system.
• Performed ultrafast hard X-ray photon correlation spectroscopy experiments at LCLS.
• Applied maximum likelihood fitting to analyze low-intensity FEL speckle patterns.

Main Results:

• Successfully split individual X-ray pulses and introduced femtosecond to nanosecond time delays.
• Measured the dynamics of gold nanoparticles suspended in hexane.
• Demonstrated reliable extraction of speckle contrast values from low-intensity data.

Conclusions:

• The split-and-delay approach is a powerful tool for dynamics measurements at Free Electron Laser (FEL) sources.
• This method facilitates the characterization of both equilibrium and reversible non-equilibrium processes.
• Enables detailed study of atomically disordered materials.