Luminescence
Encyclopedia
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 reaction
s, 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
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
by a substance not resulting from heat; it is thus a form of cold body radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
. It can be caused by chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
s, electrical energy, subatomic motions, or stress
Stress (physics)
In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
on a crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
. This distinguishes luminescence from incandescence
Incandescence
Incandescence is the emission of light from a hot body as a result of its temperature. The term derives from the Latin verb incandescere, to glow white....
, 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
- BioluminescenceBioluminescenceBioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
, emission by a living organism - Chemiluminescence, a result of a chemical reactionChemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
- ElectrochemiluminescenceElectrochemiluminescenceElectrochemiluminescence or electrogenerated chemiluminescence is a kind of luminescence produced during electrochemical reactions in solutions. In electrogenerated chemiluminescence, electrochemically generated intermediates undergo a highly exergonic reaction to produce an electronically excited...
, a result of an electrochemical reaction
- Electrochemiluminescence
- CrystalloluminescenceCrystalloluminescenceCrystalloluminescence is the effect of luminescence produced during crystallization.The abstract of an article by B. P. Chandra, V. Kalia and S. C. Datt of Rani Durgavati University , entitled Crystalloluminescence: a new tool to determine the critical size of a crystal nucleus, states:-Sources:*...
, produced during crystallizationCrystallizationCrystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid... - ElectroluminescenceElectroluminescenceElectroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field...
, a result of an electric current passed through a substance- CathodoluminescenceCathodoluminescenceCathodoluminescence is an optical and electrical phenomenon whereby a beam of electrons is generated by an electron gun and then impacts on a luminescent material such as a phosphor, causing the material to emit visible light. The most common example is the screen of a television...
, a result of being struck by an electron
- Cathodoluminescence
- MechanoluminescenceMechanoluminescenceMechanoluminescence is light emission resulting from any mechanical action on a solid. It can be produced through ultrasound, or through other means.* Fractoluminescence is caused by stress that results in the formation of fractures....
, a result of a mechanical action on a solid- TriboluminescenceTriboluminescenceTriboluminescence is an optical phenomenon in which light is generated when material is pulled apart, ripped, scratched, crushed, or rubbed through the breaking of chemical bonds in the material. The phenomenon is not fully understood, but appears to be caused by the separation and reunification...
, 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
- PiezoluminescencePiezoluminescencePiezoluminescence is a form of luminescence created by pressure upon certain solids. This phenomenon is characterized by recombination processes involving electrons, holes and impurity ion centres Some piezoelectric crystals give off a certain amount of piezoluminescence when under pressure, as...
, produced by the action of pressure on certain solids
- Triboluminescence
- PhotoluminescencePhotoluminescencePhotoluminescence is a process in which a substance absorbs photons and then re-radiates photons. Quantum mechanically, this can be described as an excitation to a higher energy state and then a return to a lower energy state accompanied by the emission of a photon...
, a result of absorption of photons- FluorescenceFluorescenceFluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
, photoluminescence in which the emitted photons are of lower energy than those absorbed - PhosphorescencePhosphorescencePhosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
, fluorescence slightly delayed after initial absorption of radiation (on a scale of seconds to hours)
- Fluorescence
- RadioluminescenceRadioluminescenceRadioluminescence is the phenomenon by which luminescence is produced in a material by the bombardment of ionizing radiation such as beta particles.-Tritium:...
, a result of bombardment by ionizing radiation - SonoluminescenceSonoluminescenceSonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound.-History:The effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. H. Frenzel and H. Schultes put an ultrasound transducer in a tank of...
, a result of imploding bubbles in a liquid when excited by sound - ThermoluminescenceThermoluminescenceThermoluminescence is a form of luminescence that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from electromagnetic radiation or other ionizing radiation is re-emitted as light upon heating of the material...
, the re-emission of absorbed light when a substance if heated
Applications
- Light-emitting diodeLight-emitting diodeA light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
s (LEDs) emit light via electro-luminescence - PhosphorPhosphorA phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s, emitting light when irradiated by higher-energy electromagnetic radiationElectromagnetic radiationElectromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
or particle radiationParticle radiationParticle radiation is the radiation of energy by means of fast-moving subatomic particles. Particle radiation is referred to as a particle beam if the particles are all moving in the same direction, similar to a light beam.... - Phosphor thermometryPhosphor thermometryPhosphor thermometry is an optical method for surface temperature measurement. The method exploits luminescence emitted by phosphor material. Phosphors are fine white or pastel-colored inorganic powders which may be stimulated by any of a variety of means to luminesce, i.e. emit light...
, measuring temperature using phosphorescence
