Surface Tension of Liquid 3He from 0.4 K down to 15 MK

Surface tension of liquid 3He has been measured using a capillary-rise method between 0.4 K and 15 mK. Data as a function of temperature T do not exhibit the T2-dependence as expected from the behaviour above 0.3 K. They deviate downwards below about 150 mK and become almost constant below 100 mK. The deviation does not depend on 4He impurity concentration nor on experimental conditions, but seems to be partly related to the decrease of the zero-point energy of the surface due to the decrease in density of the liquid.