络合物形成对电子-声子耦合的影响

Effect of complex formation on the electron-phonon coupling of all-trans-β-carotene iodine solution

测量了室温(20°C)条件下极性溶剂1,2-二氯乙烷-碘溶液中的β胡萝卜素紫外-可见吸收光谱和拉曼光谱.结果表明,生成络合物的β胡萝卜素在460 nm处的紫外-可见吸收峰消失,并在1000 nm处出现β胡萝卜素与碘形成络合物的吸收峰,致使514.5 nm激光激发时察觉不到络合物中β胡萝卜素离子CC键的共振拉曼光谱.而溶液中没有形成络合物的β胡萝卜素CC键拉曼散射截面随络合物浓度增加而减小,拉曼光谱线宽增加,π电子-声子耦合系数增加,其机理是随络合物增加溶液混乱程度增加、β胡萝卜素分子结构有序性减小所致,且可以用"相干弱阻尼电子-晶格振动"、"有效共轭长度"、"振幅模型"等理论给予解释.

The uv-vis absorption and resonance Raman spectra of all-trans-^-carotene in polar solvent 1, 2-dichloroethane with iodine are measured at 293 K. The results indicate that the absorption peak of all-trans-13-carotene in the complex disappears at 460 nm and instead a new peak of the complex formed by all-trans-13-carotene and iodine is found at 1000 nm, so that the all-trans-/3-carotene within the complex cannot produce the resonance Raman spectrum by 514.5 nm excitation laser. The Raman scattering cross section of CC bonds of all-trans-~6-carotene taht does not form in complex decreases, its full bandwidth broadens and electron-phonon parameter increases with the increase of concentration of the complex, because when the concentration of the complex increases, the disorder increases in the solution and the molecular structural order decreases. These phenomena are analyzed using the coherent weakly damped electron-lattice vibration mode, the effective conjugation length mode as well as the theory of amplitude mode in this work.