ABSTRACT
Fermi resonance phenomenon exists in simple compounds and it also widely exists in vibration spectra of complex. The complex can be formed by adding up simple compounds. As a result, the characteristic parameters of some parts of molecule will make changes, and the molecular spectra have a significant change along with it. Benzoquinone and proline in the solution form charge-transfer complex under certain conditions, but the spectra intensity is weak, our research uses Teflon liquid-core optical fiber technology to gain high quality resonance Raman spectra. We acquire Raman spectra of Benzoquinone and its complex in experiments, and analyze the characteristic parameters of Fermi resonance according to J. F. Bertran quantum theory. The results shows that, because of the formation of complex, Fermi resonance peak of C==0 bond shifts to high wavelength, the spectra intensity decreases, the frequency space increases, the coupling coefficient increases. The explanation is that, in the solution of complex, proline is donor, while benzoquinone is acceptor, the non-bonding electron of N atom which is belong to proline transfers to the pi anti-bonding orbital of benzoquinone, then n-pi* charge transfer complex is produced. That causes the change of molecular energy level, changes the Raman spectra. All these researches provide new idea and clue for spectral line certification and attribution of complex molecules, complexes and polymer.
ABSTRACT
In the present paper, an innovative experiment was done. The authors measured the Raman spectra of CS2 mixed with THF at different volume fractions. According to the J. F. Bertran theory, we analyzed the changing regularity of v1-2v2 Fermi resonance along with the different concentration. It was shown that the characteristic parameters of Fermi resonance in solution, such as spectra intensity, frequency space, coupling coefficient and anharmonic constant, will make changes along with solution concentration variation. Because of the existing of solvent effects, the spectra intensity decreases gradually, and the coupling coefficient increases gradually. The explanation of such changes is that the vibration spectra are affected not only by scattering coefficient, but also by more weak hydrogen bond's formation. In addition, the asymmetric frequency shift of the Raman spectra was also found in the paper. The fundamental frequency v1 basically has no shifts, but the overtone frequency 2v2 moves towards the high wave number gradually, which is inconsistent with the theory of symmetrical movement. According to the study of molecular microcosmic action, the formation and mechanism of the weak hydrogen bond can preferably explain the above phenomenon. The research has a major influence on the further study of solvent effects in Fermi resonance. And the paper will also provide certain reference value for the study of molecule vibration spectra in solution.
