Luminescence

UV-photoluminescence in microbiological diagnostics

Luminescence is the "spontaneous emission of radiation from an electronically excited species (or from a vibrationally excited species) not in thermal equilibrium with its environment", according to IUPAC definition. A luminescent object is emitting "cold light", in contrast to "incandescence", where an object only emits light after heating. Generally, emission of light is due to the movement of electrons between different energy levels within an atom after excitation by external factors. However, the exact mechanism of light emission in "vibrationally excited species" is unknown, as seen in sonoluminescence.

There are various ways to make an object emit light, such as by light (photoluminescence), chemical reactions (chemiluminescence), electrical energy (electroluminescence), ultrasound vibrations (sonoluminescence), and by ionising radiation (radioluminescence).

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

  • Photoluminescence, a result of the absorption of photons
    • Fluorescence, traditionally defined as the emission of light that ends immediately after the source of excitation is removed. As the definition does not fully describe the phenomenon, quantum mechanics is employed where it is defined as there is no change in spin multiplicity from the state of excitation to emission of light.
    • Phosphorescence, traditionally defined as persistent emission of light after the end of excitation. As the definition does not fully describe the phenomenon, quantum mechanics is employed where it is defined as there is a change in spin multiplicity from the state of excitation to the emission of light.
  • Chemiluminescence, the emission of light as a result of a chemical reaction
  • Crystalloluminescence, produced during crystallization
  • Electroluminescence, a result of an electric current passed through a substance
  • 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
  • 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

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.

History

The term "luminescence" was first introduced in 1888.

See also


This page was last updated at 2023-04-17 17:56 UTC. Update now. View original page.

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