Lambda point: Difference between revisions
Content deleted Content added
Rominandreu (talk | contribs) m typo retouch |
m Journal cites:, added 1 PMID using AWB (12150) |
||
| Line 1: | Line 1: | ||
[[File:Lambda transition.svg|thumb|250px|The plot of the specific heat capacity versus temperature.]] |
[[File:Lambda transition.svg|thumb|250px|The plot of the specific heat capacity versus temperature.]] |
||
The '''Lambda point''' is the [[temperature]] at which normal fluid [[helium]] (helium I) makes the transition to [[superfluid]] helium II (approximately 2.17 [[Kelvin|K]] at 1 [[atmosphere (unit)|atmosphere]]). The lowest pressure at which He-I and He-II can coexist is the vapor−He-I−He-II [[triple point]] at {{convert|2.1768|K|C}} and {{convert|5.048|kPa|atm|abbr=on}}, which is the "saturated [[vapor pressure]]" at that temperature (pure helium gas in thermal equilibrium over the liquid surface, in a [[Hermetic seal|hermetic]] container).<ref name=Donnelly>{{cite journal| title=The Observed Properties of Liquid Helium at the Saturated Vapor Pressure | first1=Russell J.| last1=Donnelly| first2=Carlo F.| last2=Barenghi |
The '''Lambda point''' is the [[temperature]] at which normal fluid [[helium]] (helium I) makes the transition to [[superfluid]] helium II (approximately 2.17 [[Kelvin|K]] at 1 [[atmosphere (unit)|atmosphere]]). The lowest pressure at which He-I and He-II can coexist is the vapor−He-I−He-II [[triple point]] at {{convert|2.1768|K|C}} and {{convert|5.048|kPa|atm|abbr=on}}, which is the "saturated [[vapor pressure]]" at that temperature (pure helium gas in thermal equilibrium over the liquid surface, in a [[Hermetic seal|hermetic]] container).<ref name=Donnelly>{{cite journal| title=The Observed Properties of Liquid Helium at the Saturated Vapor Pressure | first1=Russell J.| last1=Donnelly| first2=Carlo F.| last2=Barenghi | journal=[[Journal of Physical and Chemical Reference Data]]| year=1998| volume=27| issue=6| pages=1217–1274| doi=10.1063/1.556028|bibcode = 1998JPCRD..27.1217D }}</ref> The highest pressure at which He-I and He-II can coexist is the [[Body-centered cubic|bcc]]−He-I−He-II triple point with a helium solid at {{convert|1.762|K|C}}, {{convert|29.725|atm|kPa|abbr=on}}.<ref name=Hoffer>{{cite journal| title=Thermodynamic properties of <sup>4</sup>He. II. The bcc phase and the P-T and VT phase diagrams below 2 K | first1=J. K.| last1=Hoffer| first2=W. R.| last2=Gardner| first3=C. G.| last3=Waterfield| first4=N. E.| last4=Phillips| journal=[[Journal of Low Temperature Physics]]| date=April 1976| volume=23| issue=1| pages=63–102| doi=10.1007/BF00117245|bibcode = 1976JLTP...23...63H }}</ref> |
||
The point's name derives from the graph (pictured) that results from plotting the [[specific heat capacity]] as a function of [[temperature]] (for a given pressure in the above range, in the example shown, at 1 atmosphere), which resembles the [[Greek language|Greek]] letter [[lambda]]. The specific heat capacity tends towards [[infinity]] as the temperature approaches the lambda point. The tip of the peak is so sharp that a critical exponent characterizing the divergence of the heat capacity can be measured precisely only in zero gravity, to provide a uniform density over a substantial volume of fluid. Hence the heat capacity was measured within 2 nK below the transition in an experiment included in a Space Shuttle payload in 1992.<ref name=JPL>{{cite journal| title=Heat Capacity and Thermal Relaxation of Bulk Helium very near the Lambda Point | first1=J.A.| last1=Lipa| first2=D. R.| last2=Swanson| first3=J. A.| last3=Nissen| first4=T. C. P.| last4=Chui| first5=U. E.| last5=Israelsson| journal=[[Physical Review Letters]]| year=1996| volume=76| issue=6| pages= |
The point's name derives from the graph (pictured) that results from plotting the [[specific heat capacity]] as a function of [[temperature]] (for a given pressure in the above range, in the example shown, at 1 atmosphere), which resembles the [[Greek language|Greek]] letter [[lambda]]. The specific heat capacity tends towards [[infinity]] as the temperature approaches the lambda point. The tip of the peak is so sharp that a critical exponent characterizing the divergence of the heat capacity can be measured precisely only in zero gravity, to provide a uniform density over a substantial volume of fluid. Hence the heat capacity was measured within 2 nK below the transition in an experiment included in a Space Shuttle payload in 1992.<ref name=JPL>{{cite journal| title=Heat Capacity and Thermal Relaxation of Bulk Helium very near the Lambda Point | first1=J.A.| last1=Lipa| first2=D. R.| last2=Swanson| first3=J. A.| last3=Nissen| first4=T. C. P.| last4=Chui| first5=U. E.| last5=Israelsson| journal=[[Physical Review Letters]]| year=1996| volume=76| issue=6| pages=944–7| doi=10.1103/PhysRevLett.76.944|bibcode = 1996PhRvL..76..944L| pmid=10061591}}</ref> |
||
== See also == |
== See also == |
||
| Line 14: | Line 14: | ||
{{states of matter}} |
{{states of matter}} |
||
| ⚫ | |||
[[Category:Threshold temperatures]] |
[[Category:Threshold temperatures]] |
||
| ⚫ | |||
Revision as of 08:39, 4 April 2017
The Lambda point is the temperature at which normal fluid helium (helium I) makes the transition to superfluid helium II (approximately 2.17 K at 1 atmosphere). The lowest pressure at which He-I and He-II can coexist is the vapor−He-I−He-II triple point at 2.1768 K (−270.9732 °C) and 5.048 kPa (0.04982 atm), which is the "saturated vapor pressure" at that temperature (pure helium gas in thermal equilibrium over the liquid surface, in a hermetic container).[1] The highest pressure at which He-I and He-II can coexist is the bcc−He-I−He-II triple point with a helium solid at 1.762 K (−271.388 °C), 29.725 atm (3,011.9 kPa).[2]
The point's name derives from the graph (pictured) that results from plotting the specific heat capacity as a function of temperature (for a given pressure in the above range, in the example shown, at 1 atmosphere), which resembles the Greek letter lambda. The specific heat capacity tends towards infinity as the temperature approaches the lambda point. The tip of the peak is so sharp that a critical exponent characterizing the divergence of the heat capacity can be measured precisely only in zero gravity, to provide a uniform density over a substantial volume of fluid. Hence the heat capacity was measured within 2 nK below the transition in an experiment included in a Space Shuttle payload in 1992.[3]
See also
References
- ^ Donnelly, Russell J.; Barenghi, Carlo F. (1998). "The Observed Properties of Liquid Helium at the Saturated Vapor Pressure". Journal of Physical and Chemical Reference Data. 27 (6): 1217–1274. Bibcode:1998JPCRD..27.1217D. doi:10.1063/1.556028.
- ^ Hoffer, J. K.; Gardner, W. R.; Waterfield, C. G.; Phillips, N. E. (April 1976). "Thermodynamic properties of 4He. II. The bcc phase and the P-T and VT phase diagrams below 2 K". Journal of Low Temperature Physics. 23 (1): 63–102. Bibcode:1976JLTP...23...63H. doi:10.1007/BF00117245.
- ^ Lipa, J.A.; Swanson, D. R.; Nissen, J. A.; Chui, T. C. P.; Israelsson, U. E. (1996). "Heat Capacity and Thermal Relaxation of Bulk Helium very near the Lambda Point". Physical Review Letters. 76 (6): 944–7. Bibcode:1996PhRvL..76..944L. doi:10.1103/PhysRevLett.76.944. PMID 10061591.
External links
| State |  | |
|---|---|---|
| Low energy | ||
| High energy | ||
| Other states | ||
| Phase transitions |
| |
| Quantities | ||
| Concepts | ||
 | This condensed matter physics-related article is a stub. You can help Wikipedia by expanding it. |