APPLICATION OF AN ATR METHOD IN RAMAN-SPECTROSCOPY

The attenuated total reflection (ATR) method in a prism/gap/metal conf iguration was used in Raman spectroscopy of molecules adsorbed on silv er to improve the detection limit. The thickness of the air gap was co ntrolled between lambda(L)/2 and 2lambda(L) (lambda(L): wavelength of the incident light) with a biaxial suspension. All the scattered light within the SPP cone was collected with a Weierstrass prism and a 1:1 objective. The enhancement factor of the Raman scattering intensity fo r the use of in- and out-coupling of the SPP was found to be 134 and 7 0 for carbon and copper-phthalocyanine (CuPc), respectively. The scatt ered light inside the SPP cone is additionally enhanced by the interfe rence in the air gap. This interference is also useful to enhance the Raman signals of the adsorbates. Nearly the same enhancement factor wa s observed for the different symmetry species of vibrations in CuPc, b ecause CuPc is randomly oriented with respect to the silver surface no rmal.