Simultaneous Measurement of Surface Tension and Kinematic Viscosity using Thermal Fluctuations (1st Report, Examination of the Surface Laser-Light Scattering Method)

A new apparatus to simultaneously measure surface tension and kinematic viscosity based on the surface laser-light scattering method has been developed. In this method, we can obtain the surface properties by heterodyne detection of the scattering light from thermally excited capillary waves (ripplon), which are typically of small amplitude (∼1 nm) and have a characteristic wavelength (∼100 μm). A diffraction grating is used in order to select the wave number of capillary waves and to produce a reference beam for heterodyne detection. The purpose of the present study is to establish surface laser-light scattering as a reliable technique for the measurement of thermophysical properties. It was found through the experimental study on water that this contact-free method has considerable potential for application to measurements under extreme conditions such as high temperature and high pressure.