WDXRF
Definition
Wavelength-dispersive X-ray fluorescence. An analyser crystal disperses fluorescence by wavelength (Bragg's law again). Slower, costlier, much higher resolution.
- Full name
- Wavelength-dispersive X-ray fluorescence
- Principle
- Analyser crystal disperses fluorescence by wavelength (Bragg's law)
- Speed
- Slower than energy-dispersive XRF
- Resolution
- Much higher than energy-dispersive XRF
Common questions
Why does WDXRF rely on Bragg's law specifically?+
The analysing crystal diffracts incoming X-rays at angles that depend on their wavelength according to Bragg's law, so rotating the crystal and detector to specific angles isolates one wavelength at a time, which is what gives WDXRF its sharp peak separation.
When would a forensic lab justify the extra cost and time of WDXRF over EDXRF?+
When a case needs to resolve trace or minor elements that would overlap in an energy-dispersive spectrum, such as separating elements with adjacent atomic numbers in a comparative glass, paint, or gunshot residue analysis, the higher resolution can outweigh the slower throughput.
Related terms
- Anode Target
- The metal block (commonly Cu, Mo or Rh) that electrons strike inside an X-ray tube to produce the X-ray beam. Choice of...
- Bragg's Law
- nλ = 2d sin(θ). A monochromatic X-ray beam diffracted off the parallel lattice planes of a crystal produces constructive interference only at...
- Characteristic X-Rays
- Sharp emission lines produced when an inner-shell vacancy in an atom is filled by an outer electron. Their energies are element-specific (Moseley's...
- Continuous (Bremsstrahlung) Radiation
- Smooth background X-ray spectrum produced when high-energy electrons decelerate in the anode. Element-independent. The 'hump' under the characteristic lines.
- D-Spacing
- The perpendicular distance between adjacent parallel planes of atoms in a crystal lattice, measured in angstroms or nanometres. Each set of planes...
- EDXRF
- Energy-dispersive X-ray fluorescence. A solid-state detector resolves the entire emission spectrum at once by photon energy. Cheap, portable, faster.
- K-Alpha Line
- The characteristic X-ray emitted when an electron drops from the L-shell to fill a K-shell vacancy. Brightest line for most elements; the...