Vibronic coupling activity in the resonance Raman spectra of alkyl benzenes

Abstract

The Raman spectra of the alkyl benzene derivatives toluene, para‐xylene, and mesitylene (1,3,5,‐trimethylbenzene) have been obtained with 212.8 nm laser radiation. This radiation is resonant with the ¹L_a excited state of these benzenoid aromatics. The dominant dipole forbidden character of this electronic transition is reflected in the resonance Raman spectra. The additional substituent‐induced dipole allowed character is clearly evident in the scattering spectra of the D_2h and C_2v derivatives as well. These results illustrate the validity of the vibronic theory of Raman scattering.