The Surface of Ice Is Like Supercooled Liquid Water.

The surface of ice has been reported to be disordered at temperatures well below the bulk melting point. However, the precise nature of this disorder has been a topic of intense debate. Herein, we study the molecular properties of the surface of ice as a function of temperatures using heterodyne-detected sum-frequency generation spectroscopy. We observe that, down to 245 K, the spectral response of the surface of ice contains a component that is indistinguishable from supercooled liquid water.