Surface tension of liquid3He down to 0.3 K

The surface tension of liquid³He was measured by determining the surface wave velocity in the temperature range from 0.32 to 3.02 K. The decrease of the surface tension from the value at 0 K can be described as 22.3T² mdyn/cm up to about 0.9 K and is quite different from that of⁴He. The extrapolated value to 0 K is 155.7±0.5 mdyn/cm. The data below 1.6 K were compared with Saam's model, where the surface tension is assumed to be given by the bulk free energy times the surface width and the quasi-two-dimensional free energy. Agreement between the data and the results calculated from the model is much improved if ripplons are taken into account. Data near the gas-liquid critical point, contrary to earlier results, show that the surface tension vanishes with a critical exponent of 1.24±0.05. This is in agreement with Widom's theory.