Interfacial Vibrational Spectroscopy of the Water Bending Mode on Ice I_h

We study the molecular-level properties of the single-crystal ice Ih surface using interface-specific sum frequency generation spectroscopy. We probe the water vibrational bend region around 1650 cm-1 of the basal plane of hexagonal ice to understand the interfacial structure from vibrational properties. As opposed to the stretch mode of ice, the bending mode response depends very weakly on temperature. The large line width of the bending mode response, relative to the response on water, is inconsistent with inhomogeneous broadening and points to ultrafast pure dephasing. The bending mode of ice provides an excellent means to study adsorbate-ice interactions and understand differences in ice and water reactivity.