| Summary: | 碩士 === 逢甲大學 === 光電科學與工程學系 === 107 === Fermi resonance of Ethylene carbonate (EC) molecules causes coupling interaction and energy transfer between ground state(v2) and overtone state(2v7), resulting in changes of coupling frequency difference (Detla0=v2-2v7) and strength ratio(R=Iv2/I2v7) of two Raman spectra. In this study, Gaussian 09 simulation and experiment data were used to compare and analyze the influence of silver nanoparticles on the cluster structure and Fermi resonance in 0.4M EC aqueous solution. Although Gaussian 09 simulation didn’t consider the Fermi resonance, but we have put forward a kind of analysis method of CDOM function model and Herzberg theory, the experimental results obtained coupling frequency offset (Detla0) and intensity ratio (R0) from the Raman spectra without the influence of the Fermi resonance, and compared with Gaussian 09 to simulate all kinds of EC molecules from microscopic structure of clusters, find the conclusion accord with each other. In addition, Gaussian 09 cannot provide overtone state information (position and intensity of spectral line), we obtain the position of overtone state through the characteristic that the frequency of overtone state 2v7 is twice the frequency of v7, and obtain R0 by using the polarization derivative provided by Gaussian 09. It was found that the clusters of EC aqueous presented a 3 cluster chain structure, while it was adsorped to one silver atom in the presence of nano-silver particles. This result was also consistent with HOMO analysis of the influence of silver particles on C=O by Gaussian 09. The Detla0 calculated by simulation of the EC cluster structure was consistent with the experimental results of CDOM fitting, and its error falls within the Scaling factor of LanL2DZ corresponding to the simulated substrate. In addition, our simulation of a single cluster also qualitatively explains why aqueous solution with a concentration of 0.4M EC has the weakest Fermi resonance strength. Moreover, 0 and R0 of the three adsorption modes of the EC cluster and the silver particles also showed a similar trend in the experiment of fitting the sizes of the three silver particles (8nm, 16nm, 22nm) with the CDOM. The results not only show that the smaller the silver particles are, the stronger the Fermi resonance.
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