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Polycapillary-optics-based micro-XANES and micro-EXAFS at a third-generation bending-magnet beamline
Geert Silversmit1, Bart Vekemans, Sergey Nikitenko
1X-ray Microspectroscopy and Imaging Research Group (XMI), Department of Analytical Chemistry, Ghent University, Krijgslaan 281 S12, B-9000 Gent, Belgium. geert.silversmit@ugent.be
Journal of Synchrotron Radiation
|February 26, 2009
Summary
A new polycapillary half-lens optic effectively focuses X-ray beams for micro-X-ray absorption spectroscopy. This system minimizes beam variations, enabling detailed analysis of elements like arsenic in plants.
Area of Science:
- Materials Science
- Analytical Chemistry
- Spectroscopy
Background:
- X-ray absorption spectroscopy (XAS) requires stable, focused X-ray beams.
- Non-fixed-exit monochromators can introduce vertical beam positional variations.
- Micro-XAS demands high spatial resolution and beam stability.
Purpose of the Study:
- To test a polycapillary half-lens optic for micro-XAS applications.
- To evaluate the optic's ability to correct for beam instability from monochromators.
- To demonstrate the system's utility in analyzing biological samples.
Main Methods:
- Utilized a polycapillary half-lens optic at a third-generation bending-magnet beamline.
- Employed a non-fixed-exit Si(111) monochromator.
- Performed transmission and fluorescence micro-XAS, including EXAFS and micro-XANES.
- Analyzed arsenic K-edge in cucumber plant tissues.
Main Results:
- Reduced vertical beam height variation from ~200 microm to ~1 microm.
- Achieved focused beam sizes (FWHM) of 12-16 microm.
- Obtained transmission efficiencies of 25-45% and intensity gains of ~2000.
- Successfully determined arsenic oxidation states and metabolic conversion in plant samples.
Conclusions:
- The polycapillary half-lens optic is effective for micro-XAS, mitigating monochromator-induced beam instability.
- The system enables high-resolution elemental analysis in biological matrices.
- This technology advances the study of trace elements and their transformations in plants.
