Wavelength dispersive X-ray spectroscopy

The wavelength dispersive X-ray spectroscopy (abbreviation: WDS or WDX ) is used to analyze the characteristic X-ray radiation that is emitted by a sample (e.g. due to being bombarded with an electron beam ). In this way, all elements with an atomic number of at least 4 ( beryllium ) can be detected. The relative detection limit for elements is 0.01 percent by weight, which corresponds to an absolute detection limit of 10 ⁻¹⁴ to 10 ⁻¹⁵  g. The method belongs to the group of X-ray spectroscopy , it is closely related to energy dispersive X-ray spectroscopy (EDS or EDX).

How the detector works

With WDS, the X-rays are broken down into their spectral components by diffraction on natural or synthetic crystals. The spectrometer is always set to a wavelength and thus the characteristic X-ray radiation of an element is analyzed. For a complete spectrum, the different wavelength ranges must be covered one after the other.

Comparison with energy dispersive X-ray spectroscopy

Compared to energy dispersive X-ray spectroscopy (EDS or EDX), which are more often found on electron microscopes , the detection sensitivity with a WDS is an order of magnitude better. At the same time, a significantly higher spectral resolution of the X-ray spectrum is achieved. The advantage of measuring with EDX, on the other hand, is the simultaneous measurement of the entire X-ray spectrum of the analyzed sample point and thus the simultaneous analysis of all elements. This means a clear time and speed advantage.

See also

• Electron beam microanalysis
• Scanning electron microscope
• X-ray fluorescence analysis

literature

• Jürgen Thomas, Thomas Gemming: Analytical Transmission Electron Microscopy: An Introduction for the Practitioner . Springer, Vienna 2013, ISBN 978-3-7091-1440-7 , chapter We use the analytical possibilities , doi : 10.1007 / 978-3-7091-1440-7 .