溶液相变对β胡萝卜素溶质的紫外-可见吸收和共振拉曼光谱的影响

测量了β-胡萝卜素溶解在环己醇中65~2℃范围内的紫外-可见吸收与共振拉曼光谱。溶液在20℃时转为固态。随着温度的降低,相变时吸收光谱产生较大蓝移。虽然相变后吸收光谱、拉曼光谱仍红移,拉曼散射截面仍增加,拉曼谱带线宽仍减小,但相变后的光谱随温度的变化却大幅增加。这主要是由于固相中的β胡萝卜素分子的π电子能隙对碳碳键振动调制作用增强所致。文中对这些物理现象给予了解释。

Effect of The Phase-transition on The Ultraviolet-visible Absorption and Resonance Raman Spectra of All-trans-β-carotene

Ultraviolet-visible absorption and resonance Raman spectra of all-trans-β-carotene dis-solved in cyclohexanol were measured in the temperature range of 65-2 ℃. The sample turns from the liquid state to the solid state at about 22 ℃. After the phase transition, the absorption spectra produce a large blue-shift. With the decreasing of the temperature, the spectra have the same phe-nomena in the solid and liquid state: the spectra are red-shift, the Raman scattering cross section ( RSCS) increases, and the Raman line width decreases. However, the rates of the red-shift ( 10 times in the liquid state) and the RSCS sharply increase with the temperature in the solid state. It indicates that these results are due to the enhanced modulation effect of the π electron energy gap on the vibration of CC bonds. In this work, we provide some explanations.