Chemical Effects in Surface-Enhanced Raman Scattering
We have investigated chemical contributions to the total enhancement in surface- enhanced Raman scattering under conditions where the electromagnetic contribution is small. On stepped and kinked silver surfaces with surface atoms of high coordination number neither chemisorption of pyridine nor enhancement is observed. On a stepped surface with moderate coordination, chemisorption is observed but there is still no enhancement of the Raman scattering. Finally, pyridine chemisorbs strongly on essentially isolated silver adatoms on a rhodium substrate and enhancements of a factor of fifty or so are observed. We have obtained the electronic spectra of the latter two silver-pyridine systems using high resolution electron energy loss spectroscopy and find no correlation between the strength of the charge transfer bands observed and the enhancement factor.
KeywordsPetroleum Argon Pyridine Auger Chemisorption
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