The emission or absorption of radiation by an electron that is unbound to an atom before and after the event. As an electron passes an ionized atom it can be accelerated or decelerated, respectively absorbing or emitting a photon in the process. Since the photon can be of any wavelength, radiation emitted in this way has a continuous spectrum. The radiation emitted in this way is a type of thermal radiation, typically emitted by a hot plasma, and is also known as thermal bremsstrahlung. It is seen in many emission nebulae.