ChemInform Abstract: RESONANCE RAMAN SCATTERING OF BENZENE AND BENZENE‐D6 WITH 212.8 NM EXCITATION

Abstract

The first resonance Raman spectra of benzene and deuterobenzene are reported. Resonance excitation with the second excited singlet transition (1B1u) is obtained with 212.8 nm radiation. These resonance Raman spectra are dominated by the overtones and combinations of the vibronically active e2g modes in this dipole forbidden transition, as well as the fundamental, overtone, and combination of ν1, the a1g ring breathing mode. All of the observed features, including relative intensities and depolarization ratios, are fully rationalized within the context of the vibronic theory once the 3N‐6 multidimensionality of the vibrational sublevels is exposed. The ν8 e2g mode is found to be the most vibronically active mode in the 1B1u transition, in agreement with all calculations. However, in contrast to these calculations, the Raman analysis finds that ν9, not ν6, is the next most vibronically active e2g mode in this transition. These results parallel the observed pattern of vibronic intensities in the 3B1u→1A1g phosphorescence spectra.