Surface phase-transition dynamics of ice probed by terahertz time-domain spectroscopy

In this paper, we present an investigation of the solid-liquid phase-transition process of ice based on terahertz time-domain spectroscopy (THz-TDS), which can precisely demonstrate the low-frequency vibrational and rotational modes in gaseous or condensed state materials. The intensity of the transmitted signal is used to characterize the interaction between the terahertz wave and the melting ice. The structure transition lead to the change of physical properties such as dielectric constant with the melting of the ice. When the temperature gradually rises, the H₂O molecules on ice surface overcome the hydrogenbond interaction and start to rotate under the driving of THz field which enhancing the interaction between water molecules and incident terahertz radiation. As H₂O is a polar molecule, a dipolar moment will be induced, which contributes to the dielectric polarization. An analysis of the intensities and dielectric constant of THz-TDS signal peaks reveals the dynamic and continuous melting process on the surface of ice at room temperature. (paper)