Explanation
The X-rays emitted by the sample being analyzed are collimated by parallel copper blades (called collimator or Soller slits), and irradiate a known single crystal at a precise angle. The single crystal diffracts the photons (Bragg's law) which are collected by a detector, usually a scintillation counter or a proportional counter.
The single crystal, the specimen, and the detector are mounted precisely on a goniometer with the distance from the source of x-rays (the specimen) and the crystal equal to the distance from the crystal to the detector. It is usually operated under vacuum to reduce the absorption of soft radiation (low-energy photons) by the air and thus increase the sensitivity for the detection and quantification of light elements (between boron and oxygen).
Modern systems contain a small number of crystals of known but differing properties, with automated changing of the crystal depending on the energy being analysed, enabling elements from the entire periodic table to be analyzed, with the exception of hydrogen, helium and lithium.
It is a convenient and sensitive method for determining the chemical constituents and composition of phases on the microscale.
Read more about this topic: Wavelength Dispersive X-ray Spectroscopy
Famous quotes containing the word explanation:
“What causes adolescents to rebel is not the assertion of authority but the arbitrary use of power, with little explanation of the rules and no involvement in decision-making. . . . Involving the adolescent in decisions doesn’t mean that you are giving up your authority. It means acknowledging that the teenager is growing up and has the right to participate in decisions that affect his or her life.”
—Laurence Steinberg (20th century)
“How strange a scene is this in which we are such shifting figures, pictures, shadows. The mystery of our existence—I have no faith in any attempted explanation of it. It is all a dark, unfathomed profound.”
—Rutherford Birchard Hayes (1822–1893)
“Auden, MacNeice, Day Lewis, I have read them all,
Hoping against hope to hear the authentic call . . .
And know the explanation I must pass is this
MYou cannot light a match on a crumbling wall.”
—Hugh MacDiarmid (1892–1978)