We study the signatures of the OH stretch vibrations at the basal surface of ice using heterodyne-detected sum-frequency generation and molecular dynamics simulations. At 150 K, we observe 7 distinct modes in the sum-frequency response, five of which have an analogue in the bulk, and two pure surface-specific modes can be identified at higher frequencies (~3530 and ~3700 cm-1). The band at ~3530 cm-1 has not been reported previously. Using molecular dynamics simulations we find that the ~3530 cm-1 band contains contributions from OH stretch vibrations of both fully coordinated interfacial water molecules and of water molecules with two donor and one acceptor hydrogen-bond.

J. Phys. Chem. Lett.
Ultrafast Spectroscopy

Smit, W., Tang, F., Nagata, Y., Sanchez, A., Hasegawa, T., Backus, E., … Bakker, H. (2017). Observation and Identifcation of a New OH Stretch Vibrational Band at the Surface of Ice. J. Phys. Chem. Lett., 8, 3656–3660. doi:10.1021/acs.jpclett.7b01295