Effective radius - Revision history

en>Tom.Reding: +{{astronomy-stub}}, +half-light contour, wikify, +==See also==, ce.

2014-12-06T18:46:42Z

+{{astronomy-stub}}, +half-light contour, wikify, +==See also==, ce.

← Older revision		Revision as of 20:46, 6 December 2014
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	~~The '''Excitation Temperature''' (<math>T_{\rm ex}</math>) is defined for a population of particles via the [[Boltzmann factor]]. It satisfies~~

	~~:<math>~~
	~~\frac{n_{\rm u}}{n_{\rm l}} = \frac{g_{\rm u}}{g_{\rm l}} \exp{(-\frac{\Delta E}{k T_{\rm ex}})}~~,
	~~</math>~~

	~~where ''n<sub>u</sub>''~~ and ~~''n<sub>l</sub>'' represent~~ the ~~number of particles~~ in ~~an upper (''e.g.'' excited)~~ and ~~lower (~~'~~'e.g.'' ground) state, and ''g<sub>u</sub>'' and ''g<sub>l</sub>'' their statistical weights respectively~~.

	~~Thus the excitation temperature is the temperature at which we would expect~~ to ~~find a system with this ratio of level populations. However it has no actual physical meaning except when~~ in ~~local thermodynamical equilibrium~~. ~~The excitation temperature can even be negative for a system with inverted levels (such~~ as a ~~[[maser]]).~~

	~~In observations of the [[21 cm line]], the apparent value of the excitation temperature is often called the "spin temperature"~~.<~~ref~~>~~{{cite doi \| 10.1086/308953}}~~<~~/ref~~>

	~~==References==~~

	~~{{reflist}}~~

	~~{{DEFAULTSORT~~:~~Spin Temperature}}~~
	[[~~Category~~:~~Temperature]~~]


	~~{{Physics-stub}}~~

en>Yobot: WP:CHECKWIKI error fixes using AWB (9241)

2013-06-09T09:26:08Z

WP:CHECKWIKI error fixes using AWB (9241)

← Older revision		Revision as of 11:26, 9 June 2013
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	~~Hi there~~, ~~I am Andrew Berryhill. For a whilst I~~'~~ve been~~ in ~~Mississippi but now I~~'~~m considering other choices~~. ~~I am truly fond of to go to karaoke but I~~'~~ve been using on new issues lately~~. ~~Invoicing is my profession~~.<br><br>~~Feel free~~ to ~~surf to my blog post :: online psychic~~ ([~~http:~~//~~koreanyelp.com/index.php?document_srl~~=~~1798&mid~~=~~SchoolNews koreanyelp.com~~])		{{refimprove\|date=November 2006}}


			The '''Excitation Temperature''' (<math>T_{\rm ex}</math>) is defined for a population of particles via the [[Boltzmann factor]]. It satisfies

			:<math>
			\frac{n_{\rm u}}{n_{\rm l}} = \frac{g_{\rm u}}{g_{\rm l}} \exp{(-\frac{\Delta E}{k T_{\rm ex}})},
			</math>

			where ''n<sub>u</sub>'' and ''n<sub>l</sub>'' represent the number of particles in an upper (''e.g.'' excited) and lower (''e.g.'' ground) state, and ''g<sub>u</sub>'' and ''g<sub>l</sub>'' their statistical weights respectively.

			Thus the excitation temperature is the temperature at which we would expect to find a system with this ratio of level populations. However it has no actual physical meaning except when in local thermodynamical equilibrium. The excitation temperature can even be negative for a system with inverted levels (such as a [[maser]]).

			In observations of the [[21 cm line]], the apparent value of the excitation temperature is often called the "spin temperature".<ref>{{cite doi \| 10.1086/308953}}</ref>

			==References==

			{{reflist}}

			{{DEFAULTSORT:Spin Temperature}}
			[[Category:Temperature]]


			{{Physics-stub}}

en>ZéroBot: r2.7.1) (Robot: Adding de:Effektiver Radius

2012-07-14T19:23:18Z

r2.7.1) (Robot: Adding de:Effektiver Radius

New page

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