Advances in Raman instrumentation
Raman spectroscopy has advanced dramatically in recent years, primarily due to the availability of more inexpensive lasers, holographic optics, high-efficiency cooled array detectors, and new data processing algorithms. One useful application of Raman is chemical imaging of surfaces, resulting in detailed structural and environmental information about molecules in a sample. The best method for performing Raman imaging experiments has been a contested issue, and this work engages in this forum by introducing a new Raman imaging technique, and comparing it to existing methods. One of the primary issues disputed regarding a preferred Raman imaging technique is the illumination geometry used. An analysis is executed using both fundamental heat transport equations and experiments to show that both illumination area and dimensionality must be equally considered. Another problem that arises in Raman spectroscopy is the occurrence of artifacts such as cosmic rays. The occurrence of these artifacts can be reduced instrumentally by shortening data collection time, but now new data processing algorithms permit cosmic ray removal after collection without distortion in a singular spectrum. Aside from imaging, the high chemical information content obtained by Raman spectroscopy is useful for studying the thermodynamics of reactions in solution. To obtain all six thermodynamic variables for a particular reaction, data must be taken at a variety of temperatures and pressures. To aid in this end, a high-pressure sample chamber is developed that can be used for acquiring not only Raman spectra, but complementary NMR spectra at a variety of temperatures and pressures. This high-pressure cell is constructed using a sapphire NMR tube which is scored at the top to facilitate connectivity to the pressure generator. The sample cell will be used for studying the intermolecular interactions of hydrophobic solvation, primarily in partitioning studies.^
Dor Ben-Amotz, Purdue University.
Chemistry, Analytical|Chemistry, Physical