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Diffraction
Inside the spectrometer,
analyzing crystals of specific lattice spacing are used to diffract the
characteristic X-rays from the sample into the detector (Fig. 1).
The wavelength of the X-rays
diffracted into the detector may be selected by varying the position of the
analyzing crystal with respect to the sample, according to Bragg’s law (nλ=2d
sin θ), where n is an integer referring to the order of the reflection; λ is
the wavelength of the characteristic X-ray; d is the lattice spacing of the
diffracting material; and θ is the angle between the X-ray and the
diffractor’s surface.
A diffracted beam occurs only
when this condition is met and therefore interference from peaks from other
elements in the sample is inherently reduced. However, X-rays from only one
element at a time may be measured on the spectrometer and the position of
the crystal must be changed to tune to another element.
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