Analytical Application of Infrared Nonlinear Spectroscopy

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This project, supported in the Analytical and Surface Chemistry Program, involves the extension of nonlinear multiresonant four wave mixing (MFWM) spectroscopy to the selected excitation of multiple vibrational transitions in the infrared spectral range. Professor John C. Wright and his students at the University of Wisconsin at Madison will use multiple infrared lasers to target selected transitions within a molecule and induce unique excitation responses reflective of the sum or difference of individual resonances. The unparalleled selectivity afforded by this technique is attributed to the wealth of infrared vibrational resonances that are coupled to chemical functional group interactions, and the concomitant capability for elimination of matrix, spectral and/or solvent interferences using the four-wave mixing approach. In addition, the inherent sharpness of vibrational transitions will allow the generation of well resolved spectra at room temperatures. Professor Wright will also extend this technique to the fingerprint region of the infrared which will allow a more detailed assessment of analyte molecular structure. Multiresonant four wave mixing nonlinear spectroscopy involves the use of multiple infrared lasers to enable the judicious selection of excitation wavelengths related to specific components in complex mixtures, chemical functionalities in biological and polymeric macromolecules, and/or conformational distinctions in well ordered systems. This technique allows both qualitative and quantitative chemical differentiation with unparalleled selectivity. This project, supported in the Analytical and Surface Chemistry Program, is at a stage where its success will require the interdisciplinary efforts of physical and analytical spectroscopists, and its mature development will benefit the characterization of advanced materials and biomacromolecules.