luminescence (redirected from Luminising)

luminescence, general term applied to all forms of cool light, i.e., light emitted by sources other than a hot, incandescent body, such as a black body radiator. Luminescence is caused by the movement of electrons within a substance from more energetic states to less energetic states. There are many types of luminescence, including chemiluminescence, produced by certain chemical reactions, chiefly oxidations, at low temperatures; electroluminescence, produced by electric discharges, which may appear when silk or fur is stroked or when adhesive surfaces are separated; and triboluminescence, produced by rubbing or crushing crystals. Bioluminescence is luminescence produced by living organisms and is thought to be a type of chemiluminescence. The luminescence observed in the sea is produced by living organisms, many of them microscopic, that collect at the surface. Other examples of bioluminescence include glowworms, fireflies, and various fungi and bacteria found on rotting wood or decomposing flesh. If the luminescence is caused by absorption of some form of radiant energy, such as ultraviolet radiation or X rays (or by some other form of energy, such as mechanical pressure), and ceases as soon as (or very shortly after) the radiation causing it ceases, then it is known as fluorescence. If the luminescence continues after the radiation causing it has stopped, then it is known as phosphorescence. The term phosphorescence is often incorrectly considered synonymous with luminescence.

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luminescence

Process by which an excited material emits light in a process not caused solely by a rise in temperature. The excitation is usually achieved with ultraviolet radiation, X rays, electrons, alpha particles, electric fields, or chemical energy. The colour, or wavelength, of the light emitted is determined by the material, while the intensity depends on both the material and the input energy. Examples of luminescence include light emissions from neon lamps, luminescent watch dials, television and computer screens, fluorescent lamps, and fireflies. See also bioluminescence; fluorescence; phosphorescence.

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luminescence

Physics

a. the emission of light at low temperatures by any process other than incandescence, such as phosphorescence or chemiluminescence

b. the light emitted by such a process

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luminescence [‚lü·mə′nes·əns]

(physics)

Light emission that cannot be attributed merely to the temperature of the emitting body, but results from such causes as chemical reactions at ordinary temperatures, electron bombardment, electromagnetic radiation, and electric fields.

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Luminescence

Light emission that cannot be attributed merely to the temperature of the emitting body. Various types of luminescence are often distinguished according to the source of the energy which excites the emission. When the light energy emitted results from a chemical reaction, such as in the slow oxidation of phosphorus at ordinary temperatures, the emission is called chemiluminescence. When the luminescent chemical reaction occurs in a living system, such as in the glow of the firefly, the emission is called bioluminescence. In the foregoing two examples part of the energy of a chemical reaction is converted into light. There are also types of luminescence that are initiated by the flow of some form of energy into the body from the outside. According to the source of the exciting energy, these luminescences are designated as cathodoluminescence if the energy comes from electron bombardment; radioluminescence or roentgenoluminescence if the energy comes from x-rays or from γ-rays; photoluminescence if the energy comes from ultraviolet, visible, or infrared radiation; and electroluminescence if the energy comes from the application of an electric field. By attaching a suitable prefix to the word luminescence, similar designations may be coined to characterize luminescence excited by other agents. Since a given substance can frequently be made to luminesce by a number of different external exciting agents, and since the atomic and electronic phenomena that cause luminescence are basically the same regardless of the mode of excitation, the classification of luminescence phenomena into the foregoing categories is only a matter of convenience, not of fundamental distinction.

When a luminescent system provided with a special configuration is excited, or “pumped,” with sufficient intensity of excitation to cause an excess of excited atoms over unexcited atoms (a so-called population inversion), it can produce laser action. (Laser is an acronym for light amplification by stimulated emission of radiation.) This laser emission is a coherent stimulated luminescence, in contrast to the incoherent spontaneous emission from most luminescent systems as they are ordinarily excited and used. See Laser, Optical pumping

A second basis frequently used for characterizing luminescence is its persistence after the source of exciting energy is removed. Many substances continue to luminesce for extended periods after the exciting energy is shut off. The delayed light emission (afterglow) is generally called phosphorescence; the light emitted during the period of excitation is generally called fluorescence. In an exact sense, this classification, based on persistence of the afterglow, is not meaningful because it depends on the properties of the detector used to observe the luminescence. With appropriate instruments one can detect afterglows lasting on the order of a few thousandths of a microsecond, which would be imperceptible to the human eye. The characterization of such a luminescence, based on its persistence, as either fluorescence or phosphorescence would therefore depend upon whether the observation was made by eye or by instrumental means. These terms are nevertheless commonly used in the approximate sense defined here, and are convenient for many practical purposes. However, they can be given a more precise meaning. For example, fluorescence may be defined as a luminescence emission having an afterglow duration which is temperature-independent, while phosphorescence may be defined as a luminescence with an afterglow duration which becomes shorter with increasing temperature. See Cathodoluminescence, Electroluminescence, Fluorescence, Phosphorescence, Photoluminescence, Thermoluminescence