X-ray Absorption Spectroscopy

X-ray Absorption Fine Structure Spectroscopy (XAFS) is a powerful technique to investigate local atomic geometry and the chemical state of the atoms of one specific element in almost any type of substance. It is particularly well suited to investigate materials that lack long-range order such as:

  • nanomaterials, amorphous and highly disordered solids (clusters, catalysts, etc…)
  • liquids, gels, molecular solutions, liquid crystals (molecular sieves, etc… )
  • molecules and macromolecules containing metallic or heavy atoms (polymers, biomolecules, etc …)

Samples with very low concentration (min. 500 ppm) can be measured in Fluorescence mode.

IMPORTANT: There is no Gas Rig System at BM14 !!!

Beamline characteristics

The following beam characteristics are taken from BM26A and are not accurate for BM14. The correct values will only be updated after the new source has been installed and the new beamline BM14 has been commissioned. Please check back periodically.

  • Incident energy range with a reasonable flux 
Si(111): 5 to 30 keV
Si(311): 30 to 45 keV
  • Flux of 1 × 1011 photons/sec
  • Energy resolution ∆E/E of 1.74 × 10-4  or ∆E = 1.7 eV at E=9.689 keV
  • Horizontal acceptance 2 mrad
  • Typical beam size at sample (H × V) 3 × 1 mm2; max possible: 8 × 1.5 mm2 
  • Step-by-step data collection with the reasonable acquisition time of 1s for optimized samples
Spatial Resolution

During an EXAFS scan, especially at lower energies (5-9 KeV), the monochromator makes a much larger movement of the Bragg angle (compared to higher energies) which causes a slight vertical displacement of the beam on the sample. A feedback system connected to a beam position monitor is used to keep the beam position fixed on the sample during the EXAFS scan by adjusting the gap between the two crystals of the monochromator.

 

Special Setups

  •  Microfocus setup with beamsize down to 10 μm

This is only possible via collaboration with Prof. Laszlo Vincze, University of Ghent, Belgium, please also consult Dipanjan Banerjee prior to proposal.

The beam line is optimised for EXAFS/XANES measurements in transmission and fluorescence mode at the moment.  

 

 

 

 

Elements accessible on BM26 A

All chemical elements written with white fonts on coloured background can be studied at the DUBBLE XAFS station (see also the Note under the image). Among them, those already studied are underlined. To get the list of EXAFS/XANES publications corresponding to a given element, click on it in the image.

 

TabAccessibleElem.png

 
Note: To measure radioactive elements, you need to come to an agreement with the ESRF Safety group long before you apply for beamtime.

 

Manual

A beamline manual will be available after the commissioning of BM14.

 

References:

  • A. M. Beale, A. M. J. van der Eerden, S. D. M. Jacques, O. Leynaud, M. G. O'Brien, F. Meneau, S. Nikitenko, W. Bras and B. M. Weckhuysen, A combined SAXS/WAXS /XAFS setup capable of observing concurrent changes across the nano-to-micrometer size range in inorganic solid crystallization processes, Journal of the American Chemical Society 128 (2006), no. 38, 12386-12387.
  • S. Nikitenko, A. M. Beale, A. M. J. van der Eerden, S. D. M. Jacques, O. Leynaud, M. G. O'Brien, D. Detollenaere, R. Kaptein, B. M. Weckhuysen and W. Bras, Implementation of a combined SAXS/WAXS/QEXAFS set-up for time-resolved in situ experiments, Journal of Synchrotron Radiation 15 (2008), 632-640.
  • Grandjean, D. et al. J. Am. Chem. Soc. 127, 14554 (2005).
  • O’Brien, M. G. et al. J. Am. Chem. Soc. 128, 11744 (2006).
  • Van Santen, R. A., Nature 444, 46 (2006).

 

If you want to know more about DUBBLE's XAFS station, please contact  Dipanjan Banerjee (Project leader).

 

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