A Rollin film, named after Bernard V. Rollin, is a 30 nm-thick liquid film of helium in the helium II state. It exhibits a "creeping" effect in response to surfaces extending past the film's level (wave propagation). Helium II can escape from any non-closed container via creeping toward and eventually evaporating from capillaries of 10−7 to 10−8 meters or greater.
Rollin films are involved in the fountain effect where superfluid helium leaks out of a container in a fountain-like manner. They have high thermal conductivity.
The ability of superfluid liquids to cross obstacles that lie at a higher level is often referred to as the Onnes-effect, named after Heike Kamerlingh Onnes. The Onnes-effect is enabled by the capillary forces dominating gravity and viscous forces.
Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the Van der Waals force. The film suffers a change in chemical potential when the thickness varies. These waves are known as third sound.
- Fairbank H.A.; Lane C.T. (October 1949). "Rollin Film Rates in Liquid Helium". Physical Review. 76 (8): 1209–1211. Bibcode:1949PhRv...76.1209F. doi:10.1103/PhysRev.76.1209.
- B.V. Rollin and F. Simon (1939). "On the "film" phenomenon of liquid helium II". Physica. 6 (2): 219–230. Bibcode:1939Phy.....6..219R. doi:10.1016/S0031-8914(39)80013-1.
- Third Sound and the Onset of Superfluidity in Unsaturated Helium Films |http://authors.library.caltech.edu/6027/1/GOOpr69.pdf}}
- Video of the property in action
- Liquid Helium,Superfluid: demonstrating Lambda point transition/viscosity paradox/two fluid model/fountain effect/Rollin film/second sound
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