Nonuniform resonance Raman effect in diphenylpolyenes

Abstract

The Raman intensities (RI) of the aromatic CH stretching vibrations (near 3000 cm⁻¹) and the ring vibrations (near 1600 cm⁻¹) have been determined for some diphenylpolyenes. Using argon ion and $\mathrm{He–Ne}$ laser excitation the RI's of the 1600 cm⁻¹ ring vibrations show the expected near‐resonance type behavior whereas the RI's of CH stretching vibrations are independent of the exciting frequencies. This result can be interpreted by assuming that the RI's of the CH stretching vibrations are determined only by a σ part of the scattering tensor, i.e., this CH bond property is independent of the π‐electron system.