Abstract：Compared with infrared, ultraviolet and Raman spectra, terahertz spectra have low energy and no harmful photoionization phenomena in the substances to be measured. With the maturation of terahertz technology, the terahertz wave has become a common wave for non-destructive testing. Many biological macromolecules have fingerprints under high-frequency light detection. THz time-domain spectroscopy is the best method for nondestructive detection of biological macromolecules. At the same time, different biological molecules show different absorption peaks in Terahertz Absorption spectra. After obtaining Terahertz Absorption Spectra of the substance to be measured, compared with standard spectra, qualitative identification of the substance to be measured can be made. On this basis, combined with data processing techniques such as least squares method and support vector machine, the quantitative analysis of measured substances based on terahertz time-domain spectroscopy can also be realized. The basic principles and methods of quantum mechanics are applied in the quantum chemical analysis method. From the electronic point of view, the approximation error of the electronic analysis theory in the analysis of systems with large molecules or atoms is small, and the density functional theory does not depend on the support of experimental data and prior knowledge. The Terahertz Absorption Spectra of amino acids can be calculated by a quantum chemistry calculation method, which can match the molecular vibration mode of terahertz absorption peaks of amino acids, provide certain reference and directivity for qualitative analysis of amino acids, and provide theoretical support for terahertz time domain spectra of samples obtained from experiments. Quantum chemistry calculation is carried out on the basis of the terahertz absorption spectra obtained from experiments. It can further verify the accuracy of the experimental results. In this paper, the Terahertz Absorption Spectra of imported threonine samples were obtained by the terahertz time domain spectroscopy system. Then, three configurations of threonine samples in the form of zwitterionic ions were constructed, and the structure optimization of each configuration was completed by quantum chemical calculation method. Finally, the Terahertz Absorption Spectra of three threonine molecular configurations were calculated. The results show that the terahertz calculation spectra of the monomer and dimer configurations are quite different from the experimental spectra, but in the high frequency band, the absorption peaks of the calculated spectra are basically in agreement with the experimeotal spectra, while the lattice configuration calculation spectra of the more comprehensive reaction of intermolecular hydrogen bond and van der Waals force are in good agreement with the experimental spectra. At the same time, the smallest structure, which is consistent with the sample structure and keeps the physical properties of threonine is the cell.
李 伟，燕 芳，王志春，刘成毫. 苏氨酸不同分子构型太赫兹吸收峰的量子化学指认[J]. 光谱学与光谱分析, 2020, 40(07): 2054-2058.
LI Wei, YAN Fang, WANG Zhi-chun, LIU Cheng-hao. Quantum Chemical Identification of Terahertz Absorption Peaks of Threonine with Different Molecular Configurations. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(07): 2054-2058.
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