利用群论理论研究16种多环芳烃(polycyclic aromatic hydrocarbons, PAHs)分子振动规律, 并对PAHs指纹区特征拉曼峰进行偏振去噪, 减少非特征拉曼峰对特征拉曼峰的干扰, 增强16种PAHs之间的拉曼辨识度。 群论分析发现16种PAHs分别属于Cs, C2v, C2h, D2h点群, 四个点群中的A′, A1, Ag, Ag类对称振动属于全对称振动, 其余对称振动为非全对称振动, 其中全对称振动均具有拉曼活性。 Gaussian 09杂化密度泛函理论计算与群论分析相结合, 发现16种PAHs全对称振动分布拉曼位移全区域, 涵盖16种PAHs基团振动模式； 全对称振动产生的波动性小, 具有一定的抗外部环境干扰能力, 稳定性相对较高, 并且其产生的拉曼峰更强。 根据全对称振动具有代表性、 稳定性、 显著性的特征, 本文将16种PAHs的全对称振动作为特征拉曼振动。 此外, 研究发现, 拉曼偏振效应与振动模对称性直接相关, 拉曼光谱的偏振效应具有增强PAHs特征拉曼峰、 降低PAHs非特征峰强度的作用。 16种PAHs通过拉曼光谱的偏振效应选择性调节作用后, PAHs特征拉曼峰信噪比可提高652%~182%, 说明利用拉曼偏振效应去除非特征拉曼峰的作用显著, 可有效降低特征峰的噪声干扰。 因此, 所建立的基于群论的PAHs分子拉曼偏振去噪方法可以改善其拉曼光谱信号质量, 提高PAHs同步拉曼光谱分析效率, 为实现16种PAHs同步拉曼光谱检测提供了理论依据。

In this paper, polycyclic aromatic hydrocarbons(PAHs)vibrations law was studied based on Group Theory, and Raman polarization reduced the interference of non-characteristics peaks in fingerprint region of PAHs which would improve the Raman discrimination among 16 PAHs. The Group Theory analysis showed that 16 PAHs assigned to Cs, C2v, C2h, D2h point group separately; A′, A1, Ag, Ag vibration modes of the four point group were fully symmetric vibration and the remaining were non-totally symmetric vibration, where fully symmetric vibration of four point groups were Raman-active. Gaussian09 hybrid density functional calculation integrated with group theory analysis indicated that: PAHs Raman spectroscopy of quantum chemical calculations achieved significant consistency with the result of group theory analysis; fully symmetric vibration distributed Raman shift throughout the region, covering all groups vibration mode; in addition, fully symmetric vibration would activated stronger Raman peak which exhibit good stability. Therefore, based on the representativeness, stability and prominence, fully symmetric vibration was set as characteristic vibrations of 16 PAHs. What’s more, the research fund that, the Raman polarization effect was directly related to vibration symmetry, thus, Raman spectroscopic polarization effects was exploited to enhance character Raman peaks and reduce non-feature peak intensity. Signal to noise ratio (SNR) of characteristic Raman peaks was ameliorated as 652%~182% through selective modulation of the Raman polarization effect. The improvement of signal quality demonstrated that the noise elimination method of Raman polarization effect which based group theory was an effective approach to improve the efficiency of the Raman synchronization analysis of PAHs. Accordingly, the method provides a theoretical basis for synchronization Raman spectroscopy determination of 16 PAHs.