ASSIGNMENT AND ANHARMONICITY ANALYSIS OF OVERTONE AND COMBINATION BANDS OBSERVED IN THE RESONANCE RAMAN-SPECTRA OF CAROTENOIDS

The resonance Raman spectra of all-trans carotenoids have been observed in the region of 5000-500 cm-1 for samples in glassy solution at 77 K and in the in vivo state at room temperature. Prominent bands in the wavenumber region higher than 2000 cm-1 are assigned to either overtones or combinations of three modes due to skeletal stretches and the CH3 in-plane rock. From the wavenumbers of the observed Raman bands, anharmonicity constants for these three modes (including cross-term constants) are obtained. It is found that, for each carotenoid studied, the cross-term anharmonicity constant between the C=C and C-C stretches is significantly larger than the other anharmonicity constants.