中文摘要：

文章从理论分析和实验研究两方面探讨了L-抗坏血酸分子在0.2～2.4 THz波段的光谱特性。应用密度泛函理论的Becke-3-Lee-Yang-Parr（B3LYP）方法计算了L-抗坏血酸分子在THz波段的振动吸收谱，同时利用THz时域光谱系统（THz-TDS）测得了L-抗坏血酸在此波段的吸收谱和折射率谱。根据理论计算结果，借助于Gaussian View软件对L-抗坏血酸的THz吸收谱进行了指认。最后将L-抗坏血酸分子和市售维生素C药片的THz吸收谱进行了比较。研究表明，L-抗坏血酸分子在THz波段存在吸收峰，理论计算结果与实验结果符合较好，且这些吸收是由分子内和分子间振动共同引起的。与市售维生素C药片的吸收谱比较表明，L-抗坏血酸的吸收峰在维生素C药片的太赫兹吸收谱中均有反映。研究结果有助于进一步理解L-抗坏血酸的生物作用，为应用THz-TDS技术进行L-抗坏血酸的定量分析提供了依据。

英文摘要：

The present paper reports the theoretical and experimental vibrational frequencies of L-ascorbic acid in the frequency range from 0. 2 to 2.4 THz respectively. The vibrational frequencies of L-ascorbic acid in the THz range were simulated by Becke-3-Lee-Yang-Parr （B3LYP） algorithm of density functional theory. Simultaneously, the absorption and refractive index spectra of L-ascorbic acid were obtained using terahertz time-domain spectroscopy （THz-TDS）. Based on the results from density functional calculations, the observed vibrational peaks were assigned with the aid of Gaussian View 3. 07. Finally, the terahertz absorption spectra of tablets of vitamin C were compared with those of L-ascorbic acid. It was found that L-ascorbic acid had some distinct fingerprint spectra in the THz region and the theoretical results were in good agreement with the experimental results. The observed vibrational peaks were induced jointly by the intramolecular and intermolecular vibrations. The absorption peaks of L-ascorbic acid could be observed in the absorption spectra of the tablets of vitamin C. Our research is helpful to understanding the role of L-ascorbic acid in biological reactions. Still, the research results show the potential of the application of THz-TDS in the quantification of L-ascorbic acid.