UV RESONANCE RAMAN STUDIES OF AROMATIC AND POLYCYCLIC AROMATIC HYDROCARBONS
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Date
1984
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Ohio State University
Abstract
In a continuing investigation of the UV resonance Raman spectra of aromatic molecules we have examined the UV resonance Raman excitation profiles of derivatives of benzene and various polycyclic aromatic hydrocarbons (PAH). In contrast to benzene which shows no resonance enhancement with excitation in its 260 nm $B_{2u}$ transition, substituted benzene derivatives such as phenol show significant enhancement and highly structured excitation profiles. UV resonance Raman excitation between 220 and 260 nm of a variety of polycyclic aromatic hydrocarbons which include naphthalene and pyrene result in very intense Raman spectra and rich excitation profiles. The intensities are sufficient to observe PAH species at less than $10^{-6}$ M concentrations. We have also examined PAH's in complex matrices such as samples of coal liquids. Different excitation wavelengths enhance the Raman spectra of different PAH ring systems. None of the samples we have studied show fluorescence interference; UV Raman spectroscopy excited below 260 nm is less susceptible to fluorescence interference than conventional visible wavelength Raman spectroscopy.
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Author Institution: Department of Chemistry, University of Pittsburgh