Surface tension of liquid4He. Surface energy of the Bose-Einstein condensate

The surface tension of liquid⁴He was measured by means of surface-wave resonance, and the relative variation showed excellent agreement with that previously obtained by a precise capillary-rise method. The absolute value of the surface tension at absolute zero was measured as 354.4±0.5 mdyne/cm, 6% smaller than the previous value. The surface energy associated with the Bose-Einstein condensate wave function was found to dominate the surface tension in the superfluid phase. The condensate fraction other than in the vicinity of the point was estimated asn₀(0)-n₀(T)=A(T/T), withn₀(0)=0.125±0.025,A=0.177±0.047, and =5.07±0.17.