Surface tension of dilute solutions of4He in3He

Abstract The surface tension of dilute solutions of 4 He in 3 He was measured by means of surface wave resonance in order to examine the effect of adding small amounts of 4 He to pure 3 He. We found that compared with pure 3 He, the surface tension of the 5.2% 4 He solution increases by 6 mdyn/cm at 1K. The increase of the surface tension means that the 4 He atoms are excluded from the surface of dilute solutions. The data below 1.6K were compared with Saam's model. Assuming that the 4 He behaves like an ideal quasiparticle gas and the 4 He quasiparticle surface scattering length is proportional to the amount of surface adsorption, the temperature dependence of the surface tension is well explained.