Li Shuo, Sun Shang, Li Zuo-wei, Qu Guan-nan, Liu Tian-yuan, Sun Cheng-lin, Fan Li-mei
State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2013 Sep;33(9):2311-4.
A visible absorption and Raman spectra of all-trans-beta-beta-carotene was measured in cyclohexanol solution in the temperature range from 68 degrees C to 26 degrees C. The results indicated that the visible absorption spectra are red-shifted, Raman scattering cross section increases, Huang-Ryes factor and electron-phonon coupling constants of CC bond vibration modes decreases with the temperature decreasing. The changes are interpreted using the theory of "coherent weakly damped electronic-lattice vibration model" and "effective conjugation length model". The red shift of the absorption spectra and intensity of the Raman active are attributed to the thermal conformational change-induced increase in the effective conjugation length in all-trans-beta-carotene chains. All-trans-beta-carotene has strong coherent weakly damped CC bonds vibrational properties, which lead to large Raman scattering cross section in the solvent of low temperature. The electron-phonon coupling constants with dimension are used, which can easily establish relation with the Huang-Rhys factor and calculate the electron-phonon coupling constants of CC bond vibration modes. Effective conjugation length, the pi-electron delocalization range and the Raman scattering cross section are described by the electron-phonon coupling constants.
在68℃至26℃的温度范围内，测量了全反式β-胡萝卜素在环己醇溶液中的可见吸收光谱和拉曼光谱。结果表明，随着温度降低，可见吸收光谱发生红移，拉曼散射截面增大，CC键振动模式的黄-里斯因子和电子-声子耦合常数减小。利用“相干弱阻尼电子-晶格振动模型”和“有效共轭长度模型”对这些变化进行了解释。吸收光谱的红移和拉曼活性的强度归因于热构象变化引起的全反式β-胡萝卜素链中有效共轭长度的增加。全反式β-胡萝卜素具有很强的相干弱阻尼CC键振动特性，这导致在低温溶剂中有较大的拉曼散射截面。使用具有量纲的电子-声子耦合常数，它可以很容易地与黄-里斯因子建立关系，并计算CC键振动模式的电子-声子耦合常数。有效共轭长度、π电子离域范围和拉曼散射截面由电子-声子耦合常数描述。
