**Free-Bound Emission** (also known as **radiative recombination**) occurs when a free electron is captured by an ion. 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.