Electrodynamical Forbiddance of Strong Quadrupole Light-Molecule   Interaction in the Methane Molecule and its Manifestation in Surface Enhanced   Hyper Raman Scattering Spectra
  It is demonstrated in the framework of the Dipole-Quadrupole theory, that strong quadrupole light-molecule interaction, which is responsible for the most enhancement of SEHRS in the methane molecule, which belongs to the symmetry group, experiences so-called electrodynamical forbiddance due to electrodynamical law, and does not influence on the formation of the SEHRS spectra. This forbiddance results in the fact that the lines, caused by the totally symmetric vibrations, transforming after the unit irreducible representation, which are observed in symmetrical molecules with another sufficiently high groups of the point symmetry, such as pyrazine and phenazine, with symmetry group, must be slight, or be absent at all. In this case in methane the most enhanced lines are those, caused by vibrations, transforming by the irreducible representation, or . 
V.P. Chelibanov, A.M. Polubotko
physics.chem-ph