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High resolution wavelength-dispersive X-Ray Fluorescence Analysis (RFA)

Brief description of the Method

In the soft X-ray range, for the determination of relevant atomic data such as transition probabilities, a high resolution detection system is needed due to the lower absolute differences in characteristic energies. Therefore, PTB built a calibrateable Wavelength-Dispersive Spectrometer (WDS) based on a spherical grating and a CCD camera. It can be used to determine atomic fundamental parameters (see fig. 1) and for highly resolving X-ray Emission Spectrometry (XES) investigations [2] also for nanolayered specimens [3].

Applications

  • Determination of atomic fundamental parameters
  • X-ray Emission Spectrometry (XES)
  • Chemical speciation [2]

Specifications

  • Energy range 78 eV – 1760 eV
  • Resolving power of about 1000

Research Highlights

  • Nickel LIII fluorescence and satellite transition probabilities determined with an alternative methodology for soft-x-ray emission spectrometry [1]
  • XES and XAFS investigations on the speciation of different Ti compounds [2]
  • X-ray emission spectrometry at nanolayered specimens [3]

 

Fig. 1: X-ray emission spectrum (black) of a nominal 0.5 µm thick Ni-foilexcited by 879 eV photons just above the LII-edge (871 eV). The fitted theoretical spectral distributions for the diagram lines (green) and satellite line (red) convoluted by experimentally determined response functions. The sum of the fitted spectral distributions is plotted in blue.

For the X-ray range from 2.3 to 18.4 keV a calibratable Initiates file downloadvon Hamos spectrometer based on two full-cylinder mosaic crystals was built at the PTB. The full cylindrical crystal geometry ensures a large solid angle of detection while the mosaic Highly Annealed Pyrolytic Graphite (HAPG) crystal provides a high integral reflectivity. The spectrometer is optimized for highest solid angle of acceptance and combines high detection efficiency with moderate to high spectral resolution in a compact and mechanically stable arrangement (see fig. 2).

Applications

  • X-ray Emission Spectrometry (XES)
  • X-ray Absorption Spectrometry (XAS)
  • Resonant X- ray Emission Spectrometry (RXES)
  • Pulsed FEL sources
  • Chemical speciation
  • Determination of atomic fundamental parameters

Specifications

  • Energy range using one crystal in the first-order reflection: 2.4 keV - 18.4 keV
  • Energy range using two crystals in the first-order reflection: 2.4 keV - 9.2 keV
  • Energy range using two crystals and second-order reflection: 9.2 keV - 18.4 keV
  • Resolving power of about 1500 using one-crystal-setup
  • Resolving power of about 2000 using two-crystals-setup

Research Highlights

  • X-ray Emission Spectroscopy (XES) on Copper and Vanadium Kα and Kβ lines at the Dipole White Light (DWL) beamline in PTB laboratory at BESSY II
  • In the experiments one, respectively two cylindrical HAPG crystals were used to disperse the XES signal onto the CCD detector
  • An increase in spectral resolution of around 40 % can be observed when using two cylinder crystals

    Fig. 1: X-ray emission spectrum of Mn Kb-edge of two kathode and one anode material, containing Mn in different states.

References

  1. Ni LIII fluorescence and satellite transition probabilities determined with an alternative methodology for soft-x-ray emission spectrometry, Physical Review A 79, 032503 (2009)
  2. Evaluation of High-Resolution X-ray Absorption, Emission Spectroscopy for the Chemical Speciation of Binary Titanium Compounds, Anal. Chem. (2009), 81, 1770–1776
  3. Focusing of Soft X-ray Radiation and Characterization of the Beam Profile enabling X-Ray Emission Spectrometry at Nanolayered Specimens, Spectrochimica Acta Part B 78 (2012) 37–41
  4. M. Gerlach et al, Characterization of HAPG mosaic crystals using synchrotron radiation, Appl. Cryst. (2015) 48(5),1381-1390