Temperature induced changes in resonance Raman spectra intensity of all-trans-β-carotene: changes in the fundamental, combination and overtone modes.
The resonance Raman spectra of the fundamental, combination and overtone modes around the CC and CC stretches of all-trans-β-carotene in 1,2-dichloroethane solution are obtained from the 293K to 83K temperature range. The results indicate that the intensity of the fundamentals in the liquid and solid phases generally increases as the temperature decreases, except for the liquid-solid phase transition, which exhibits a decreasing trend. The Raman intensities ratio between the fundamentals υ1 and υ2, combinations (overtones) and the fundamentals both increases with decreasing temperature. The Raman bandwidths of the CC bonds gradually become narrow as the temperature decreases. These varieties of relative intensity are analyzed using the coherent weakly damped electron-lattice vibration mode, the effective conjugation length mode as well as the theory of electron-phonon interaction in this work.