Electromagnetic radiation that occurs when charged particles with energies large compared to their rest energies are decelerated over a very short distance. Since electrons are much lighter than protons, electron bremsstrahlung is the most common. In bremsstrahlung, a continuous spectrum with a characteristic profile and energy cutoff (i.e., wavelength minimum) is produced. In addition, lines can appear super imposed, corresponding to the ejection of K and L shell electrons knocked out of atoms in collisions with the high-energy electrons.

For the continuous bremsstrahlung spectrum, equate the quantities
[
where is the charge on the electron, V is the voltage change, h is Planck's constant, c is the speed of light, and is the minimum possible wavelength of radiation. Solving for then gives
[
The cross section for an electron to be observed in a solid angle is given by



where and are the initial and final velocities, respectively and is the range of wavenumbers. In the soft-photon limit, , and for scattering angle . In this limit, each of the last two integrals are given by


The first integral can be reduced to





This can be expanded in a series as
[
so combining ,,and gives
[
in the nonrelativistic limit (Bjorken and Drell 1964, pp. 126-127).

A line spectrum occurs when electrons are knocked out from low shells and electrons from higher shells drop down.