|
|
| Line 1: |
Line 1: |
| {{redirect|Phosphorescent|the indie rock band|Phosphorescent (band)}}
| | Jerrie is what you can call me but I don't like when regular people use my full company. My hubby and I chose to call home in Massachusetts. What I love doing are to play croquet together with now I have time period to take on issues. The job I've been occupying to find years is an portion clerk. See what's new on a few website here: http://circuspartypanama.com<br><br>My site [http://circuspartypanama.com clash of clans hacker download] |
| {{dablink|In common use, phosphorescence also refers to the emission of light by [[bioluminescent]] plankton, and some other forms of [[chemoluminescence]].}}
| |
| [[File:Phosphorescence.jpg|thumb|Phosphorescent bird figure]]
| |
| [[File:Phosphorescent.jpg|thumb|Phosphorescent powder under visible light, ultraviolet light, and total darkness]]
| |
| [[File:Fused silica phosphorescence from a 24 million watt flash.jpg|thumb|An extremely intense pulse of UV light in a [[flashtube]] produced this blue phosphorescence in the [[fused silica]] envelope.]]
| |
| [[File:Microflash-quartz-phosphorescence.jpg|thumb|Phosphorescence of the quartz ignition tube of an [[air-gap flash]]]]
| |
| | |
| '''Phosphorescence''' 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 mechanism|forbidden]]" [[energy level|energy state]] transitions in [[quantum mechanics]]. As these transitions occur very slowly in certain materials, absorbed radiation may be re-emitted at a lower intensity for up to several hours after the original excitation.
| |
| | |
| Commonly seen examples of phosphorescent materials are the glow-in-the-dark toys, paint, and clock dials that glow for some time after being charged with a bright light such as in any normal reading or room light. Typically the glowing then slowly fades out within minutes (or up to a few hours) in a dark room.<ref>Karl A. Franz, Wolfgang G. Kehr, Alfred Siggel, Jürgen Wieczoreck, and Waldemar Adam "Luminescent Materials" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a15_519}}</ref>
| |
| | |
| The study of phosphorescent materials led to the [[Radioactivity#Discovery|discovery of radioactivity]] in 1896.
| |
| | |
| Ironically, [[allotropes of phosphorus|white phosphorus]] (from which phosphorescence takes its name) does not actually exhibit this property, but rather [[chemiluminescence]].
| |
| | |
| ==Explanations==
| |
| ===Simple ===
| |
| In simple terms, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. This is in some cases the mechanism used for "glow-in-the-dark" materials which are "charged" by exposure to light. Unlike the relatively swift reactions in a common fluorescent tube, phosphorescent materials used for these materials absorb the energy and "store" it for a longer time as the processes required to re-emit the light occur less often.[[File:Fluo-phosopho.jpg|thumb|300px|left|Energy scheme used to explain the difference between fluorescence and phosphorescence]]
| |
| | |
| ===Quantum mechanical===
| |
| [[File:Electronic Processes Involving Light.png|thumb|After an electron absorbs a photon of high energy, it may undergo vibrational relaxations and intersystem crossing to another spin state. Again the system relaxes vibrationally in the new spin state and eventually emits light by phosphorescence.]]
| |
| | |
| Most photoluminescent events, in which a chemical substrate absorbs and then re-emits a [[photon]] of light, are fast, on the order of 10 [[nanosecond]]s. Light is absorbed and emitted at these fast time scales in cases where the energy of the photons involved matches the available energy states and allowed transitions of the substrate. In the special case of phosphorescence, the absorbed photon energy undergoes an unusual [[intersystem crossing]] into an energy state of higher ''spin multiplicity'' (''see [[term symbol]]''), usually a [[triplet state]]. As a result, the energy can become trapped in the triplet state with only classically "forbidden" transitions available to return to the lower energy state. These transitions, although "forbidden", will still occur in quantum mechanics but are [[chemical kinetics|kinetically]] unfavored and thus progress at significantly slower time scales. Most phosphorescent compounds are still relatively fast emitters, with triplet lifetimes on the order of milliseconds. However, some compounds have triplet lifetimes up to minutes or even hours, allowing these substances to effectively store light energy in the form of very slowly degrading excited electron states. If the phosphorescent [[quantum yield]] is high, these substances will release significant amounts of light over long time scales, creating so-called "glow-in-the-dark" materials.
| |
| | |
| ====Equation====
| |
| :<math>S_0 + h\nu \to S_1 \to T_1 \to S_0 + h\nu^\prime\ </math>
| |
| where S is a [[singlet state|singlet]] and T a [[spin triplet|triplet]] whose subscripts denote states (0 is the ground state, and 1 the excited state). Transitions can also occur to higher energy levels, but the first excited state is denoted for simplicity.
| |
| | |
| ==Chemiluminescence==
| |
| {{main|Chemiluminescence}}
| |
| Some examples of "glow-in-the-dark" materials do not glow by phosphorescence. For example, "[[glow sticks]]" glow due to a [[chemiluminescent]] process which is commonly mistaken for phosphorescence. In chemiluminescence, an excited state is created via a chemical reaction. The light emission tracks the kinetic progress of the underlying chemical reaction. The excited state will then transfer to a "dye" molecule, also known as a [[sensitizer]] or [[fluorophor]], and subsequently fluoresce back to the ground state
| |
| | |
| ==Materials==
| |
| Common pigments used in phosphorescent materials include [[zinc sulfide]] and [[strontium aluminate]]. Use of zinc sulfide for safety related products dates back to the 1930s. However, the development of strontium aluminate, with a luminance approximately 10 times greater than zinc sulfide, has relegated most zinc sulfide based products to the novelty category. Strontium aluminate based pigments are now used in exit signs, pathway marking, and other safety related signage.<ref>Zitoun, D.; Bernaud, L.; Manteghetti, A. Microwave Synthesis of a Long-Lasting Phosphor. J. Chem. Ed. 2009, 86, 72-75.{{DOI|10.1021/ed086p72}}</ref>
| |
| | |
| <gallery widths="220" heights="120" perrow="3" caption="Phosphorescent pigments - comparison ZnS vs. aluminate">
| |
| File:Phosphorescent pigments.jpg|left: Zinc sulfide, right: SrAl<sub>2</sub>O<sub>4</sub>
| |
| File:Phosphorescent pigments 1 min.jpg|pigments in the dark
| |
| File:Phosphorescent pigments 4 min.jpg|pigments in the dark after 4 min
| |
| </gallery>
| |
| | |
| <gallery widths="160" heights="120" perrow="4" caption="Phosphorescent pigments red and blue"> | |
| File:Phosphorescent pigment red.JPG|phosphorescent pigment red (Calcium sulfide)
| |
| File:Phosphorescent pigment red dark.JPG|phosphorescent pigment red in the dark
| |
| File:Phosphorescent pigment blue.JPG|phosphorescent pigment blue (alkaline earth metal silicate )
| |
| File:Phosphorescent pigment blue dark.JPG|phosphorescent pigment blue in the dark
| |
| </gallery> | |
| | |
| {{Expand section|date=October 2008}}
| |
| | |
| ==See also==
| |
| * [[Luminous paint]]
| |
| * [[Microsphere]]
| |
| * [[Persistent luminescence]]
| |
| * [[Phosphor]]
| |
| * [[Phosphoroscope]]
| |
| * [[Tritium]]
| |
| | |
| ==References==
| |
| {{Reflist}}
| |
| | |
| ==External links==
| |
| {{Wiktionarypar|phosphorescence|glowing}}
| |
| *[http://www.kronometric.org/article/lume/#4.0 Luminosity in Watches]
| |
| | |
| [[Category:Luminescence]]
| |
| [[Category:Spectroscopy]]
| |
Jerrie is what you can call me but I don't like when regular people use my full company. My hubby and I chose to call home in Massachusetts. What I love doing are to play croquet together with now I have time period to take on issues. The job I've been occupying to find years is an portion clerk. See what's new on a few website here: http://circuspartypanama.com
My site clash of clans hacker download