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Characteristic X-rays
Intermediate
Produced by inner-shell transitions.
√f ∝ (Z−b)When an inner-shell electron is knocked out and an outer electron drops in, an X-ray of fixed energy is emitted, e.g. K_α. These lines are unique to the element.
Copper K_α = 8.05 keV (0.154 nm).
They sit on top of the continuous spectrum.
In more detail
Characteristic X-rays are emitted when electrons fall into inner shells of an atom, giving photons with energies specific to the element. They form sharp lines in X-ray spectra.
Real-world uses
- X-ray fluorescence analysis identifies elements in samples.
- Medical and industrial X-ray analysis uses characteristic lines.
- Engineers use characteristic X-rays in X-ray fluorescence to identify the elements in an alloy or archaeological sample.
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Frequently asked questions
How are they produced?
By removing an inner electron and then letting an outer electron fill the gap.
Why are they element specific?
Because the energy levels depend on the nuclear charge.
Why do these X-rays have fixed energies?
They come from electron transitions between inner shells, whose energies depend on the element.
Related topics in Atomic & Nuclear Physics
Absorption and emission spectra · Ionisation energy · Franck–Hertz experiment · Continuous X-ray spectrum · Moseley's law · X-ray diffraction