Fundamental Physics Experiment Resolves Controversy Regarding Helium Surface Tension

A controversy has existed in the physics literature about the correct value for the surface tension of liquid helium, with different groups having obtained results for this important quantity that differ by as much as 6%. To resolve this issue, the group at Brown University headed by Humphrey Maris has developed a novel method to measure the surface tension utilizing drop levitation techniques employed in their ground-based task. A drop of liquid helium is levitated using the magnetic field from a superconducting solenoid. Oscillatory motion of the isolated drop is then excited by means of an electrostatic drive and the frequencies of different normal modes of oscillation are measured. From these frequencies, the surface tension of the liquid helium in the drop can be determined with high accuracy. This measurement settles the uncertainty about the correct value of the surface tension of liquid helium, with the value they derive for the surface tension agreeing precisely with one of the published results. Their paper "Surface Tension of Liquid 4He as Measured Using the Vibration Modes of a Levitated Drop", with authors C. Vicente, W.-J. Yao, H.J. Maris and G.M. Seidel, has been accepted for publication in Physical Review B and will appear this fall.