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Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. The most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can only be seen when exposed to UV light. However, unlike phosphorescence, where the substance would continue to glow and emit light for some time after the radiation source has been turned off, fluorescent materials would cease to glow immediately upon removal of the excitation source. Hence, it is not a persistent phenomenon. Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, cosmic-ray detection, and, most commonly, fluorescent lamps. Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. ==History== An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and in 1565 by Nicolás Monardes in the infusion known as ''lignum nephriticum'' (Latin for "kidney wood"). It was derived from the wood of two tree species, ''Pterocarpus indicus'' and ''Eysenhardtia polystachya''. The chemical compound responsible for this fluorescence is matlaline, which is the oxidation product of one of the flavonoids found in this wood.〔 In 1819, Edward D. Clarke and in 1822 René Just Haüy〔Haüy merely repeats Clarke's observation regarding the colors of the specimen of fluorite which he (Clarke) had examined: Haüy, ''Traité de Minéralogie'', 2nd ed. (Paris, France: Bachelier and Huzard, 1822), vol. 1, (p. 512 ). Fluorite is called "chaux fluatée" by Haüy: "... violette par réflection, et verdâtre par transparence au Derbyshire." ((color of fluorite is ) violet by reflection, and greenish by transmission in (from ) Derbyshire.)〕 described fluorescence in fluorites, Sir David Brewster described the phenomenon for chlorophyll in 1833〔 On page 542, Brewster mentions that when white light passes through an alcoholic solution of chlorophyll, red light is reflected from it.〕 and Sir John Herschel did the same for quinine in 1845. In his 1852 paper on the "Refrangibility" (wavelength change) of light, George Gabriel Stokes described the ability of fluorspar and uranium glass to change invisible light beyond the violet end of the visible spectrum into blue light. He named this phenomenon ''fluorescence'' : "I am almost inclined to coin a word, and call the appearance ''fluorescence'', from fluor-spar (fluorite ), as the analogous term ''opalescence'' is derived from the name of a mineral."〔 From page 479, footnote: "I am almost inclined to coin a word, and call the appearance ''fluorescence'', from fluor-spar, as the analogous term ''opalescence'' is derived from the name of a mineral."〕 The name was derived from the mineral fluorite (calcium difluoride), some examples of which contain traces of divalent europium, which serves as the fluorescent activator to emit blue light. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight and observed blue light emitted by an ethanol solution of quinine exposed by it.〔Stokes (1852), pages 472–473. In a footnote on page 473, Stokes acknowledges that in 1843, Edmond Becquerel had observed that quinine acid sulfate strongly absorbs ultraviolet radiation (i.e., solar radiation beyond Fraunhofer's H band in the solar spectrum). See: Edmond Becquerel (1843) ("Des effets produits sur les corps par les rayons solaires" ) (On the effects produced on substances by solar rays), ''Comptes rendus'', 17 : 882–884; on page 883, Becquerel cites quinine acid sulfate ("sulfate acide de quinine") as strongly absorbing ultraviolet light.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「fluorescence」の詳細全文を読む スポンサード リンク
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