Parametric instability of a liquid-vapor interface close to the critical point

An experimental study of the parametric instability of a liquid-vapor interface close to the critical point is presented. A cell containing carbon dioxide at the critical density is vertically vibrated sinusoidally; the acceleration amplitude a₀ and the instabiilty wavelength λ₀ at the instabiilty onset are measured with respect to the excitation frequency and the critical temperature difference Tc-T. These measurements provide a simple way to determine the surface tension and the density difference between the two phases. When Tc-T diminishes λ₀ decreases and reaches a finite value whereas a₀ diverges. The shape of the wave pattern appears to depend on Tc-T.