ENHANCED RAMAN SPECTRA OF SMALL MOLECULES ABSORBED TO A SILVER SURFACE
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Date
1980
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Ohio State University
Abstract
We report the observation of the enhanced Raman spectra of molecules absorbed to the surface of a silver mirror. Typical experiments, including the sample preparation, are done at 12 K and the absorbants include CO, $NH_{3}$, ethylene, propylene and cis-2-butene. The Raman spectra include bands of both the surface absorbed molecules and of the bulk molecules. The surface bands are generally broader and shifted to lower frequency as compared to the bulk bands. As the thickness of the absorbent film is increased, the bulk spectra becomes more intense while the surface spectra remain constant. The intensity enhancement factor for the surface bands is as high as $10^{6}$ but is not the same for all enhanced bands of a given molecule. The intensity enhancement and frequency shift for bands corresponding to a particular vibrational mode give clues to the nature of the surface bonding. Enhanced Raman spectra were observed for all excitation wavelengths of an argon ion laser and for dye laser wavelengths available between 580 and 600 nm.
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