Full-field fluorescence mode micro-XANES imaging using a unique energy dispersive CCD detector

Area of Science:

• Materials Science
• Spectroscopy
• Chemistry

Background:

• X-ray absorption near-edge structure (XANES) spectroscopy is a key technique for determining chemical states and local structures.
• Current full-field transmission mode XANES is limited to thin, concentrated samples for spatially resolved imaging.
• Developing methods for analyzing thicker samples is crucial for broader applications.

Purpose of the Study:

• To present a novel approach for full-field fluorescence mode XANES using an energy dispersive (ED) pnCCD detector (SLcam).
• To overcome the sample thickness limitations of traditional XANES imaging.
• To demonstrate spatially resolved chemical state mapping on larger sample areas with microscopic resolution.

Main Methods:

• Utilized a unique energy dispersive (ED) pnCCD detector, the SLcam, for fluorescence mode XANES.
• Performed full-field XANES experiments without scanning the sample.
• Acquired XANES profiles for thousands of points in a single measurement.

Main Results:

• Significantly relaxed sample thickness constraints for XANES imaging.
• Achieved spatially resolved chemical state information on millimeter-sized sample areas.
• Demonstrated proof of concept using a Fe(0)/Fe2O3 model and a Nitisol soil sample for iron chemical state distribution.

Conclusions:

• The SLcam detector enables fluorescence mode micro-XANES, expanding applicability to thicker samples.
• This method allows for rapid, high-resolution chemical state mapping over large areas.
• The technique provides valuable insights into chemical state distribution in complex samples like soil.