Production of bremsstahlung when an electron decelerates through interaction with an atom. Image credit: European Nuclear Society.
Bremsstrahlung is electromagnetic radiation, notably X-rays, given off by fast-moving charged particles, such as electrons, when they are slowed down by passing through matter. "Bremsstrahlung" is German for "braking radiation." Bremsstrahlung has energy that varies continuously from zero up to the energy of the incident electrons; it therefore exhibits a continuous spectrum.