Tensile strength of liquidHe4

Experiments to measure the tensile strength of liquids have often failed to reach the predicted value, presumably due to the onset of heterogeneous nucleation. Since it seemed impossible to completely eliminate all heterogeneous nucleation, we adopted a strategy that minimized its effect. A piezoelectric transducer in the form of a hemispherical shell was used to focus a short burst of ultrasound into a small volume of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. The onset of cavitation was detected by the scattering of laser light. The experimental results both above and below the λ transition are in agreement with homogeneous-nucleation theory for a nucleation rate of approximately ${10}^{15}$ critical-size bubbles/s ${\mathrm{cm}}^3$. An apparent lowering of the tensile strength near the extension of the λ line into the metastable liquid is noted and discussed. This experiment extends the range of confirmation of the theoretically predicted tensile strength of liquids to a reduced pressure eight times further into the negative-pressure region than previous studies in any other liquid.