中文摘要：

本文测量了全反式β胡萝卜素在二甲基亚砜中81–25 ℃ 范围的紫外–可见吸收和拉曼光谱. 结果表明, 随温度降低, 紫外–可见吸收光谱、拉曼光谱都发生红移, 拉曼光谱线型变窄, 散射截面增加这些现象的发生是由于随温度降低, β胡萝卜素分子的热无序降低、分子结构有序性增加、π电子离域扩展, 有效共轭长度增加, 分子的电子能隙变窄. 另外, 随着温度的降低, 溶剂密度增加, 由Lorentz-Lorenz 关系得知相伴的折射率增加, 从而引起吸收光谱的红移. CC键键长增加, 使CC 键拉曼光谱红移; 振动弛豫时间变长, 各CC 键之间的键长差减小, 线宽变窄; 但由于声子, π电子耦合加强使CC键拉曼线型不对称程度增加, 低频端＂肩＂扩展, CC键的弱阻尼相干振动增加, 使拉曼散射截面增加.

英文摘要：

The effects of temperature on the visible absorption and Raman spectra of all-trans-β-carotene dissolved in dimethyl sulfoxide at temperatures ranging from 81 ℃ to 18 ℃ were determined. The bands of the visible absorption and Raman spectra of all-trans-β-carotene showed red blue shifts. The bandwidth of the Raman spectra becomes narrow. Raman scattering cross-section increases as the temperature decreases. The red shift of the absorption spectrum is attributed to the thermal conformational change-induced decrease in the effective conjugation length in all-trans-β-carotene chains. The molecular structural order increases and the π-electron delocalization range is extended as the temperature decreases. The red shift in all-trans-β-carotene can be also attributed to the decrease in the liquid density, and the concomitant decrease in the refractive index is shown by the Lorentz-Lorenz relation. The apparent behavior of the temperature-induced band broadening of CC bonds can be associated with the decrease of difference in C-C and C=C bond lengths, and the shorter vibrational relaxation time. The shoulder observed below 1520 cm-1 shows a red shift. The enhancement of coherent weakly-damped CC stretching vibrations may increase the Raman scattering cross-section.