Plasma recombination is a process by which positive ions of a plasma capture a free (energetic) electron and combine with electrons or negative ions to form new neutral atoms (gas). The process of recombination can be described as the reverse of ionization, whereby conditions allow the plasma to evert to a gas. Recombination is an exothermic process, meaning that the plasma releases some of its internal energy, usually in the form of heat. Except for plasma composed of pure hydrogen (or its isotopes), there may also be multiply charged ions. Therefore, a single electron capture results in decrease of the ion charge, but not necessarily in a neutral atom or molecule.