The emission of radiation when a free electron (one unattached to an atom) is captured by an ion; also known as radiative recombination. The capture (recombination) may be to the ground state, in which case a photon with an energy greater than the ionization potential of the ion or atom is emitted, producing a band of continuous emission (a continuous spectrum). Alternatively, the recombination may be to an excited energy level, with the emission of a photon, after which the electron cascades down through the excited states to the ground state, producing emission lines characteristic of that ion or atom. See also Recombination Line.
Subjects: Astronomy and Astrophysics.