Design and Implementation of a Nonlinear Interferometer

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In this project, funded by the Chemical Measurements and Imaging Program of the Chemistry Division, Professor Mary Jane Shultz of Tufts University will conduct a research program that seeks to develop and implement a versatile, generally applicable, nonlinear interferometer. The interferometer is based on nonlinear spectroscopy, sum frequency generation (SFG); a potentially powerful, surface-specific vibrational spectroscopy. Currently tapping the power of SFG is thwarted by the nonlinear nature of SFG, challenging spectral interpretation. Recently developed techniques hold promise for linearizing the spectrum, but are hampered by instrumental complexity and protocol implementation resulting in large uncertainties. Based on similar linear interferometers, the new design is expected to result in a three orders-of-magnitude accuracy improvement. Improved accuracy is particularly critical of aqueous solution interfaces. Thus, the new instrument will be applied to three systems: acetonitrile-water, ammonia-water, and ice-air. These three systems are each of interest in their own right: Acetonitrile-water is a common chromatography solvent, ammonia is the only significant basic atmospheric gas and is the source of particulate matter for cloud condensation nuclei via neutralization of acidic gases, and ice literally shapes the world. The research will construct a new instrument that allows unprecedented resolution for probing weak but important hydrogen-bond interactions. Understanding these interactions is essential for understanding the complex interplay between water and a variety of interfaces including cell membranes and other biological materials, atmospheric pollutants, and minerals in the Earth's crust. The project will be performed with the assistance of a post-doctoral associate accompanied by undergraduate students including women and members of underrepresented minorities. All will receive technical training in cutting-edge spectroscopic tools. In addition to these activities, the Shultz group is an active participant in the departmental COOP (Chemistry Organized Outreach Program) designed to both bring front-line research to local secondary schools and to bring promising secondary students to the University for hands-on experience.