The Lambda point is the temperature below which normal fluid helium (helium I) transitions to superfluid helium II (approximately 2.17 K at 1 atmosphere). The lowest pressure lambda point is at 2.172 K, 0.0497 atm and highest pressure to achieve superfluidity, the "upper point", is at 1.76 K, 29.8 atm.
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.
Famous quotes containing the word point:
“Constancy in love is of two sorts: One is the effect of new excellencies that are always presenting themselves afresh, and attract our affections continually; the other is only from a point of honor, and a taking of pride not to change.”
—François, Duc De La Rochefoucauld (1613–1680)