Luminescence

Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light".

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 dials, hands, scales, and signs of aviation and navigational instruments and markings are often coated with luminescent materials in a process known as "luminising".

Types

The following are types of luminescence:
* Chemiluminescence, the emission of light as a result of a chemical reaction
** Bioluminescence, a result of biochemical reactions in a living organism
**Electrochemiluminescence, a result of an electrochemical reaction
**Lyoluminescence, a result of dissolving a solid (usually heavily irradiated) in a liquid solvent
**Candoluminescence, is light emitted by certain materials at elevated temperatures, which differs from the blackbody emission expected at the temperature in question.
* Crystalloluminescence, produced during crystallization
* Electroluminescence, a result of an electric current passed through a substance
**Cathodoluminescence, a result of a luminescent material being struck by electrons
*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
**Sonoluminescence, a result of imploding bubbles in a liquid when excited by sound
* Photoluminescence, a result of absorption of photons
**Fluorescence, photoluminescence as a result of singlet–singlet electronic relaxation (typical lifetime: nanoseconds)
**Phosphorescence, photoluminescence either as a result of triplet–triplet electronic relaxation or of persistent luminescence (typical lifetime: microseconds to hours)
* Radioluminescence, a result of bombardment by ionizing radiation
*Thermoluminescence, the re-emission of absorbed energy when a substance is heated
**Cryoluminescence, the emission of light when an object is cooled (an example of this is wulfenite)

Applications

*Light-emitting diodes (LEDs) emit light via electro-luminescence.
* Phosphors, materials that emit light when irradiated by higher-energy electromagnetic radiation or particle radiation
*Laser, and lamp industry
*Phosphor thermometry, measuring temperature using phosphorescence
*Thermoluminescence dating
* Thermoluminescent dosimeter
*Non-disruptive observation of processes within a cell.

Luminescence occurs in some minerals when they are exposed to low-powered sources of ultraviolet or infrared electromagnetic radiation (for example, portable UV lamps), at atmospheric pressure and atmospheric temperatures. This property of these minerals can be used during the process of mineral identification at rock outcrops in the field, or in the laboratory.

See also

* List of light sources
*Scientific American,
Luminous Paint
(historical aspects), 10-Dec-1881, pp.368

References

External links

Fluorophores.org A database of luminescent dyes

{{Authority control

Light sources
1880s neologisms