Angular and polarization dependence of surface-enhanced Raman scattering in attenuated-total-reflection geometry

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Abstract
Polarization and angle-of-incidence dependences of the surface-enhanced Raman scattering (SERS) signal of benzoic acid adsorbed on isolated oblate particles of silver have been measured in an attenuated-total-reflection geometry. Simultaneously, the absorption of photons in the particles has been determined by a photoacoustic method. At the critical angle and in the wavelength range of the present study, only one dipole resonance mode, the nonazimuthally symmetric mode, is excited by the component of the electric field parallel to the reflecting surface. This has allowed us to evaluate contributions of the resonance absorption and the nonresonant intrinsic absorption to the total absorption. We show that the absorption of p-polarized light at the critical angle is solely due to the intrinsic absorption. No Raman signal can be detected in the absence of the surface-plasmon mode or electromagnetic resonance. We show also that the dependence of SERS on the polarization and angle of incidence can be explained by considering only the excitation of localized plasmons.