Electrodynamical forbiddance of strong quadrupole light–molecule interaction and peculiarities of the SEHR spectra in the methane molecule

It is demonstrated that the strong quadrupole light–molecule interaction, which is responsible for the most enhancement of Surface Enhanced Hyper Raman Scattering (SEHRS), experiences so-called electrodynamical forbiddance in the methane molecule and molecules with cubic symmetry groups and does not influence on formation of the SEHRS spectra. This forbiddance results in the fact that the lines, caused by the totally symmetric vibrations, which are observed in pyrazine and phenazine, must be slight, or absent at all. In this case, in methane, the most enhanced lines are those, caused by vibrations, transforming after the irreducible representations T 1 , or T 2 .