饱和一元醇远红外光谱的测试及仿真研究

用衰减全反射傅里叶光谱仪(FTIR-ATR)在室温条件下测试了甲醇、乙醇、丙醇、异丙醇、丁醇及异丁醇六种饱和一元醇在30～300 cm-1波段的远红外透射光谱。通过分析这六种具有类似化学结构的一元醇的远红外透射光谱，发现它们在30～150 cm-1波段均有明显的吸收峰，但在150～300 cm-1波段吸收峰不明显; 羟基在一元醇中的质量百分比越高，相关一元醇的远红外光谱的平均透过率越低; 直链一元醇的光谱平均透过率高于支链状的同分异构体。采用密度泛函理论B3LYP/6-311G(d,p)基组对甲醇单体和多聚体进行结构优化和频率计算。计算显示，在30～150 cm-1波段甲醇单体分子没有出现吸收峰，但是甲醇的多聚体则出现明显的吸收峰，计算得到的多聚体吸收峰位置与实际测量的结果相符合。结果表明，甲醇在太赫兹波段吸收的来自于不同形式聚合体的集体振动，甲醇溶液以甲醇三聚体为主要的存在形式。本成果不仅为研究有机分子在太赫兹波段的频率响应提供了新的实验方法，而且对进一步利用FTIR-ATR研究其他有机分子具有借鉴意义。

Characterization and Simulation of Far-Infrared Spectroscopy for Saturated Monohydric Alcohols

Fourier transform infrared-attenuated total reflection (FTIR-ATR) was employed to measure the far-infrared (FIR) spectra in wavenumbers of 30～300 cm-1 for six kinds of saturated monohydric alcohols, namely: methanol, ethanol, propanol, isopropanol, butanol and isobutanol. Further analysis of the FIR spectra for these monohydric alcohols with similar chemical structures reveals that absorption peaks are observed obviously for these alcohols in the 30～150 cm-1 band, whereas not obvious peaks are measured in the 150～300 cm-1 band. Moreover, it was found that the monohydric alcohols with higher hydroxy concentration possess lower average FIR transmission. In addition, the average FIR transmissions of linear chain monohydric alcohols are higher than those of the branched chain ones. Furthermore, the density functional theory (DFT) B3LYP/6-311G(d,p) basis set was employed to simulate the structures optimization and to calculate the responding frequencies of the methanol monomer and polymer. Simulation result indicates that no absorption peaks are found in the 30～150 cm-1 band for the methanol monomer molecule, whereas there are obvious absorption peaks for the methanol polymers in the same band. In addition, the simulated absorption peak positions for the methanol polymers are in agreement with those experimentally measured. Both results indicate that the absorption of the methanol in Terahertz (THz) is attributed to the collective vibrations of different kinds of polymer, and that the polymer for methanol is mainly trimmer. This paper not only provides a new way to investigate the responding frequencies of organic molecule in THz band, but also is helpful for the FTIR-ATR study of other organic molecules.