Abstract
A number of studies on collective dynamics of hydrogen bonded liquids, such as water and methanol, with high-resolution inelastic X-ray scattering (IXS) have been reported for the last decade. The IXS technique has become a powerful tool owing to third-generation X-ray synchrotron radiation facilities. The dynamical transition of water from hydrodynamic behavior to viscoelastic one at the Q that was predicted by MD simulation was experimentally revealed by the IXS technique. The positive dispersion of dynamical velocity of sound of supercritical water (SCW) and methanol (SCM) drastically changes with density, reflecting cluster formation in them. The IXS results reveal the dynamic features in SCW and SCM, which are consistent with the previous structure data obtained from the diffraction and spectroscopic methods.
