The First Observation of Low-Frequency Raman Spectra of Supercritical Water

Abstract

Low-frequency Raman spectra of liquid water from −250 to 250 cm⁻¹ towards to and above the supercritical point have been observed and analyzed by using the multiple random telegraph model (MRT) relaxation function. The 180 cm⁻¹ band has vanished with increasing temperature with constant pressure at 25 MPa. This is due to the destruction of hydrogen-bonds. The obtained relaxation time first decreases and then increases from about 260°C (433 K) with increasing temperature toward to the supercritical state. This behavior is consistent with that of the dielectric relaxation time.