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Research

Ice

Ice is arguably the most important solid in the universe: In addition to shuttling countless substance in outer space, it sculpts the surface of the Earth and processes molecules in the stratosphere, e.g. ozone hole forming molecfules, and on terra firma, e.g. the HONO bloom each spring from the Artic ice. Particularly for understanding the latter two, the configuration of water molecules in the ice surface is very important. Yet, until recently, the surface of this marvelous solid was a mystery. There are two reasons for this incomplete picture: locating the hydrogen atoms is extremely challenging and preparing a surface that is amenable to molecular-level investigation is a demanding task.

Sum frequency generation is an excellent tool for detecting hydrogen atoms in water the challenge lies in interpreting the spectra. Addition of PAN analysis provides a methodology to deconvolute the complex spectrum into its components. Further, PAN analysis enables assignment of at least two modes in addition to the dangling OH. The origin of these modes is labeled in the ice model pictured above.

Identification of these modes would not be possible without an excellent ice substrate. We therefore, developed, designed, and built a specialty apparatus to grow large samples of single-crystal ice. Using these crystals, we can prepare surfaces with a defect density on the order of 500/cm2. (For reference the best single-crystal Si and Ge surfaces used in the semiconductor industry have a defect density on the order of 100/cm2).



Single-crystal ice
 

Cryogenic
single-crystal ice

Basal face ice
 

Prism face ice
 

Recent Research on Ice >

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