Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a substance as a result of heating. Historically, radioactivity was thought of as a form of "radio-luminescence", although it is today considered to be separate since it involves more than electromagnetic radiation. The term 'luminescence' was introduced in 1888 by Eilhard Wiedemann.
The dials, hands, scales and signs of aviation and navigational instruments and markings are often coated with luminescent materials in a process known as 'luminising'.
The following are types of luminescence
- Chemiluminescence, a result of a chemical reaction
- Bioluminescence, emission as a result of biochemical reaction by a living organism
- Electrochemiluminescence, a result of an electrochemical reaction
- Crystalloluminescence, produced during crystallization
- Electroluminescence, a result of an electric current passed through a substance
- Cathodoluminescence, a result of being struck by an electron
- Mechanoluminescence, a result of a mechanical action on a solid
- Triboluminescence, generated when bonds in a material are broken when that material is scratched, crushed, or rubbed
- Fractoluminescence, generated when bonds in certain crystals are broken by fractures
- Piezoluminescence, produced by the action of pressure on certain solids
- Photoluminescence, a result of absorption of photons
- Fluorescence, photoluminescence as a result of singlet–singlet electronic relaxation (typical lifetime: nanoseconds)
- Phosphorescence, photoluminescence as a result of triplet–singlet electronic relaxation (typical lifetime: milliseconds to hours)
- Radioluminescence, a result of bombardment by ionizing radiation
- Sonoluminescence, a result of imploding bubbles in a liquid when excited by sound
- Thermoluminescence, the re-emission of absorbed light when a substance is heated
Read more about Luminescence: Applications