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Latest Research on the Prism Face of Ice

We have recently determined that the 3400 cm-1 feature visible in the ppp basal face spectrum, and the ppp prism face spectra can be assigned to three bonding motifs on the surface of single crystal ice. Our most recent publication about ice describes these results in some detail. Here’s the abstract from our latest paper1:

The prism face of single crystal ice Ih has been studied using sum frequency vibrational spectroscopy focusing on identification of resonances in the hydrogen-bonded region. Several modes have been observed at about 3400 cm-1; each mode is both polarization and orientation dependent. The polarization capabilities of sum frequency generation (SFG) are used in conjunction with the crystal orientation to characterize three vibrational modes. These modes are assigned to three-coordinated water molecules in the top-half bilayer having different bonding and orientation motifs.

Experimental evidence for a particular vibrational mode assignment is rather rare in the water research community. Although the hydrogen bonding region in the IR spectrum of water and ice has been an active topic of research for quite some time now, the broadness of the region, and multiple overlapping modes has made un-ambiguous, experimentally grounded, mode assignment a tall order. Most of the time, one can only make inferences based on computational modeling and sound physical chemistry principals. Curve fitting a measured spectrum and making estimates of what vibrational modes "might" be responsible is typical of what has been done. In this instance however, we were able to provide strong experimental evidence for these mode assignments based upon spectroscopy. We used the unique capabilities of SFG to aid us in these mode assignments. SFG is sensitive to molecular orientation with respect to the surface and the laboratory reference frame, laser polarization, molecular polarizability and change in electric dipole. Because single crystal ice is highly ordered, bonding motifs are limited in number and can be explicitly explored by using the full capabilities of SFG.

1) Bisson, P. J.; Shultz, M. J. Hydrogen Bonding in the Prism Face of Ice Ih via Sum Frequency Vibrational Spectroscopy. J. Phys. Chem. A 2013." [doi]

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