RAMAN-SCATTERING BY HIGH-DENSITY DISPERSIONS .2. CALCULATION OF SURFACE-ENHANCED RAMAN-SCATTERING FROM CO AND BENZENE PHYSISORBED ON PAIRS OF PARTICLES OF AG, PT, GE, AND SIO

In part I, a mathematical formalism was developed for calculating Rama n scattering intensities from a collection of spherical particles unif ormly coated with molecules, and applied to the special case of two CO -coated Ag particles in contact, with their centers aligned with the l aser field and under parallel polarization conditions. In this paper, the additional relations required to perform the calculations for arbi trary orientation and polarization conditions are developed and used i n calculations for CO and benzene physisorbed onto pairs of particles of Ag, Pt, Ge, and SiO. The large increase in Raman radiation intensit y per molecule, reported in part I on going from a one-particle to a t wo-particle system, is shown here to apply only to the Raman radiation component polarized parallel to the interparticle axis and due to the incident radiation component similarly polarized. For all other compo nents, the excitation spectra are similar for the two systems. The lar ge increase for the parallel-parallel case is due to the process in wh ich the primary Raman multipoles centered on one particle induce Raman dipoles on the pair of particles.