Thermal radiation method: proposal of a new technique for measuring interfacial or surface fluctuations

A thermal radiation method is proposed as a new technique for measuring interfacial or surface fluctuations. From Kirchhoff's law, the intensity includes diffuse scattering, which means that it can be used to measure mesoscopic fluctuations of samples like a small-angle X-ray or neutron scattering method. We applied the method to mercury on a sapphire system where the mercury wets the sapphire by a first-order phase transition (prewetting) at high temperature and high pressure, and thus large fluctuations in the film can be expected in its supercritical region. We succeeded in measuring huge surface fluctuations in the film.