Luminescence is a process by which a molecule loses energy through the emission of visible or invisible radiation, unaccompanied by high temperature. The emission may result from the absorption of exciting energy in the form of photons, charged particles, or chemical change.

Chemiluminescence is a special case of luminescence in which the excitation source is a chemical reaction. One important chemiluminescent processes discovered during the middle of the last century involves the oxidation of the organic molecule luminol by hydrogen peroxide (H₂O₂) in the presence of Fe(CN)₆^3-. A green-blue light is emitted. Other well known chemiluminescent systems are based on the decomposition of esters of oxalic acid.Hydrogen peroxide acts as a catalyst to form an energy-rich decomposition product of the ester. This energy can be transferred to a fluorescer, which then emits light. In the case of green lightsticks, an oxalate ester and fluorescer...