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The following is a graph of the intensity of Bremsstrahlung generated by accelerating electrons to hit a target vs. its wavelength.

I'm wondering what causes the additional peaks for high energies? I have read in my physics script and on Wikipedia that "these peaks are characteristic of the material used as target", but what exactly is going on at the level of atoms?

Does the electron maybe go into some sort of bound state and thus loses - in addition to its kinetic energy - also some potential energy? Why would that only happen for high enough energies?

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The Bremsstrahlung spectrum is a continuous spectrum because it comes from the continuous deceleration of the electron in the field of the atoms, in the case of your figure. The photons take away the energy of the decelerating electron.

There also exists a large quantum mechanical probability that the electron scatters an electron out from the filled shells of the atoms in the target, creating a hole in the shell. The hole is filled by an electron falling back in and releasing a photon with the characteristic line for the target.The energy of these photons depend on the material and are in the higher energy parts the more bound the ejected electron was.

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Thank you for answering! This makes sense. =) Also thanks for the link, @dmckee. –  Sam Feb 2 '12 at 0:19
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