Structure of solid-water interfaces at supercritical conditions

X-Ray reflectivity is a powerful method to investigate thin layer structures at interfaces, especially at the solid-liquid interface. With a suited sample environment, this method can be applied in situ at high pressures and high temperatures. At octadecyl-trichorosilane (OTS) coated surfaces, an electron density depleted region, the so-called hydrophobic gap, is a phenomenon that was widely studied in literature in the past. Even now, after several years of discussion, the origin of the hydrophobic gap is not fully understood. Especially the behaviour of the hydrophobic gap under extreme conditions is largely unexplored. With the proposed experiment, we will observe the development of the hydrophobic gap on a molecular scale at the transition to the supercritical water state for the first time.