REGULARITIES OF THE SER SPECTRA OF SYMMETRICAL MOLECULES

On the basis of the SERS (Surface Enhancement of Raman Scattering) the ory proposed by the author, a theory of the SER (Surface Enhancement R aman) spectra of symmetrical molecules is developed. The concept of ma in and minor moments for symmetrical molecules is introduced. It is de monstrated that the full scattering in a spectral line consists of som e contributions caused by the scattering via various dipole and quadru pole moments. A qualitative classification of the contributions after the enhancement degree, based on the concept of the main and minor mom ents is made. On the basis of group theory, selection rules for these contributions are obtained. It is demonstrated that some bands, caused by the vibrations, transforming by the unitary irreducible representa tion are most pronounced in SERS. The lines caused by the vibrations, transforming as the d(z) moment, are also pronounced. It is pointed ou t that strong bands, usually forbidden in Raman scattering, can appear . The SER spectra of concrete symmetrical molecules ethylene, pyridine , PIMH, PIMK are considered. The theoretical results obtained fit the experimental results for these spectra and support the significance of the strong dipole and quadrupole light-molecule interactions in SERS.