1. Environmental Research Academy, North China Electric Power University, Beijing 102206, China
2. MOE Key Laboratory of Resources Environmental Systems Optimization, North China Electric Power University, Beijing 102206, China
Abstract：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.
Key words：PAHs; Group theory; Polarized Raman; Synchronization analysis
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