The Analytical and Surface Chemistry Program supports Professor Peter Chen at Spelman College to develop and utilize high resolution coherent 2D spectroscopy to study molecular systems too complex for existing spectroscopic techniques. Also under study are small but important molecules (e.g., EPA priority pollutants like NO2 and SO2) for which strong perturbations and mixing effects yield spectra too complicated to study using existing (one-dimensional) spectroscopic techniques. Dr. Chen and his group develop new coherent two-dimensional spectroscopic techniques to deal with these problems and to study the dynamics of important photochemical processes in the atmosphere.
The project may improve fundamental understanding of the photochemistry of NO2 and SO2, which are among the six priority pollutants targeted by the Clean Air Act. It provides exceptional research training of African American women at one of only two Historically Black Colleges for women.
Spectroscopy, the use of light to study matter, has and continues to be one of the most successful techniques for studying matter and energy. For example, our understanding of atmospheric pollution and processes, high-tech materials, and many biomedical systems has relied heavily upon the use of spectroscopy to determine the size, shape, structure, and behavior of molecules. For some molecules (especially larger ones), spectroscopy has been ineffective because the results have been too complicated (i.e., the spectra are severely congested). This congestion impedes the analysis of spectra; it makes it difficult to find key patterns needed to analyze the results. Furthermore, many systems contain a mixture of molecules, and mixtures also tend to yield severely congested spectra. As a result, many of the easy-to-analyze spectra have been taken and analyzed, leaving a very large number of cases that have been considered far too congested to analyze. Our work has focused on the development of high resolution coherent 2D spectroscopy as a technique for overcoming the limitations caused by congestion in gas phase electronic spectra. Unlike conventional forms of spectroscopy, our technique makes pattern identification and analysis very fast and easy, even for molecules that normally yield spectra that were previously thought to be impossibly congested. As we continued to work on this 2D technique, we realized that congestion was often still a problem even after expansion from one-dimension to two-dimensions. During this project, we developed a three-dimensional version that can be use to further improve congestion problems that persist in the second dimension. We are beginning to think that the persistent congestion in the second dimension will prove to be ubiquitous for larger molecules. We believe that our techniques provide the tools necessary to perform and analyze results from spectroscopy experiments of previously problematic larger molecules and mixtures.
