Probing the molecular basis for solvent-induced dephasing using resonance Raman spectroscopy: betaine-30 in CH3OH, CH3OD, and CD3OD

Absolute Raman cross-sections are reported for fourteen normal modes of betaine-30 dye in CH3OH, CH3OD, and CD3OD solution, at five different excitation frequencies within the visible absorption band. Consistent with previous results from our lab, the Raman intensities of betaine-30 in CD3OD solution are generally stronger than in CH3OH solution. For most of the betaine-30 normal modes, however, the resonance Raman cross-sections are similar in CH3OD and CH3OH solution. The results suggest that methyl group motion, more so than hydroxyl group motion, is responsible for dephasing of the resonant electronic transition of betaine-30 in methanol.