/floo res"euhns, flaw-, floh-/, n. Physics, Chem.
1. the emission of radiation, esp. of visible light, by a substance during exposure to external radiation, as light or x-rays. Cf. phosphorescence (def. 1).
2. the property possessed by a substance capable of such emission.
3. the radiation so produced.
[1852; FLUOR(SPAR) + -ESCENCE, on the model of OPALESCENCE, in reference to the mineral's newly discovered property]

* * *

Emission of electromagnetic radiation, usually visible light, caused by excitation of atoms in a material, which then reemit almost immediately (within about 10-8 seconds).

The initial excitation is usually caused by absorption of energy from incident radiation or particles, such as X rays or electrons. Because re-emission occurs so quickly, the fluorescence ceases as soon as the exciting source is removed, unlike phosphorescence, which persists as an afterglow. A fluorescent lightbulb is coated on the inside with a powder and contains a gas; electricity causes the gas to emit ultraviolet radiation, which then stimulates the tube coating to emit light. The pixels of a television or computer screen fluoresce when electrons from an electron gun strike them. Fluorescence is often used to analyze molecules, and the addition of a fluorescing agent with emissions in the blue region of the spectrum to detergents causes fabrics to appear whiter in sunlight. X-ray fluorescence is used to analyze minerals.

* * *

Universalium. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • fluorescence — [ flyɔresɑ̃s ] n. f. • 1856; mot angl. (1852), de fluor, d apr. phosphorescence ♦ Phys. Luminescence d une substance (solide, liquide ou gaz) due à une transition spontanée des molécules, d un état excité vers l état fondamental. Fluorescence… …   Encyclopédie Universelle

  • Fluorescence — Flu o*res cence, n. [From {Fluor}.] (Chemistry, Optics) A luminescence emitted by certain substances due to the absorption of radiation at one wavelength, and the almost instantaneous re emission of radiation at another, usually longer wavelength …   The Collaborative International Dictionary of English

  • fluorescence — 1852, glowing in ultraviolet light, coined by English mathematician and physicist Sir George G. Stokes (1819 1903) from fluorspar (see FLUORINE (Cf. fluorine)), because in it he first noticed the phenomenon, + ESCENCE (Cf. escence), on analogy of …   Etymology dictionary

  • fluorescence —  Fluorescence  Флуоресценция   Кратковременная люминесценция. Излучательный переход между двумя состояниями одинаковой мультиплетности (синглетными или триплетными уровнями). Флуоресценция наблюдается в жидкой, твердой и газовой фазах. При… …   Толковый англо-русский словарь по нанотехнологии. - М.

  • fluorescence — ► NOUN 1) light emitted by a substance when it is exposed to radiation such as ultraviolet light or X rays. 2) the property of emitting light in this way. ORIGIN from FLUORSPAR(Cf. ↑F) (which fluoresces), on the pattern of opalescence …   English terms dictionary

  • fluorescence — [flo͞o΄ə res′əns] n. [< FLUOR(SPAR) + ESCENCE] 1. the property of a substance, such as fluorite, of producing light while it is being acted upon by ultraviolet rays, X rays, or other forms of radiant energy 2. the production of such light 3.… …   English World dictionary

  • Fluorescence — Fluorescent minerals emit visible light when exposed to ultraviolet light Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength.[1] It is a form of luminescence.… …   Wikipedia

  • Fluorescence X — Spectrométrie de fluorescence X Pour les articles homonymes, voir SFX, FX et XRF. Un spectromètre de fluorescence X Philips PW1606 avec manutention automatiq …   Wikipédia en Français

  • Fluorescence — La fluorescence est une émission lumineuse provoquée par l excitation d une molécule (généralement par absorption d un photon) immédiatement suivie d une émission spontanée. Ce processus est différent de la phosphorescence. La fluorescence peut… …   Wikipédia en Français

  • fluorescence — (flu o rè ssan s ) s. f. Terme de physique. Éclairement particulier que présentent certaines substances lorsqu elles sont exposées à l action des parties les plus réfrangibles de la radiation lumineuse, c est à dire à l action des rayons… …   Dictionnaire de la Langue Française d'Émile Littré

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”