Indiana Section of the Society for Applied SpectroscopyIndiana Section of the Society for Applied Spectroscopy
1999-2000 Seminar Abstracts
TWO DIMENSIONAL COHERENT VIBRATIONAL SPECTROSCOPY USING THE OPTICAL ANALOGUE TO 2D-NMR
Dr. John C. Wright
Department of Chemistry, University of Wisconsin, Madison, WI 53706
Traditional spectroscopic methods are based on incoherent processes that involve population changes but it is also possible to perform spectroscopy using coherent processes. Ever since the invention of the laser, there has been a dream to develop the optical analogues to NMR spectroscopy because of its capabilities for probing detailed structural questions. In particular, the development of the optical analogue to 2D NMR methods would provide a powerful new measurement tool to probe intra- and intermolecular interactions. In this talk, we will describe the successful development of the optical analogue to 2D NMR and we will show its unique capabilities for achieving spectral selectivity. The approach uses four wave mixing where three lasers are focused into a sample and new beams are generated by nonlinear processes. Their intensity depends upon whether there are vibrational resonances with the three lasers. We have named these methods Doubly Vibrationally Enhanced Four Wave Mixing (DOVE-FWM). These methods are related to the traditional methods of infrared and Raman spectroscopy but they are capable of dissecting vibrational spectra into the components that make them up. They are the equivalent of a spectroscopic separation. Furthermore, they are capable of isolating the vibrational features that are associated with intra-and intermolecular interactions, line narrowing lines that are broadened by H-bonding, and freezing the molecular motion to obtain snap-shots of the local environment.
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