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.
ABSTRACT
The Raman scattering coefficients of the fundamental v1 (992 cm(-1)) of C6 H6 and the fundamental v1 (656 cm(-1) ) of CS2 changed dramatically with relative concentration of the binary solution of CS2 and C6 H6. The Raman spectra of the binary solution with different relative concentrations were measured. The results show that both the v1 fundamentals intensities changed dramatically with the relative concentration of the solution and the fundamental v1 of C6 H6 has little effect on the Fermi resonance v1 +v6-v8. On the contrary, the change in the v1 fundamental intensity of the CS2 changed which has more effect not only on the Fermi resonance v1 - 2v2 but also on the v2 fundamental. In this report, the experimental results were analyzed based on the J. F. Bertran theory and group theory.
ABSTRACT
Raman spectra of liquid carbon disulfide (CS) and carbon tetrachloride (CCl4) were measured. And the spectral intensity was analyzed using the J. F. Bertran theory and the group theory. The rule about Fermi resonance was obtained from the Raman spectra of carbon disulfide (CS) and carbon tetrachloride (CCL4): (1) The energy can transfer between a fundamental and an overtone frequency about Fermi resonance; the two spectra have the same intensity. The spectral intensity of the two spectra was equal (R=1) about Fermi resonance, when the difference between fundamental of Fermi resonance and overtone of Fermi resonance was very small. (2) The intensity of overtone is stronger than that of fundamental's. (3) The spectrum of Fermi resonance was observed, but the fundamental frequency was not. This article has very good reference value for the assignments in the molecular structure and the research of contents.
ABSTRACT
The binary systems of 1,1,3,3-tetramethylurea (TMU) with water, TMU with methanol, TMU with ethanol and N,N-dimethylformamide(DMF) with water were measured by Raman method. With the analysis of the frequency changes of stretching vibration of carboxyl with concentration the authors found that the frequency shift underwent two processes: first, the frequency of stretching vibration of carboxyl down shifts with the increase in hydrogen-bond acceptor concentration; secondly, when the concentration of binary system surpasses a critical value, the wave number remains almost constant, and only the rela tive intensity changes. Through this critical volume ratio, the authors found that the large self-associated water molecule was in volved in the TMU aqueous binary system; while the small self-associated molecule or dimer formation was present in other binary systems.
ABSTRACT
Raman spectra of 1,1,3,3-tetramethylurea in 20 solvents were obtained to investigate the solute-solvent interactions and to correlate solvent properties such as the Kirkwood-Bauer-Magat (KBM)equation, the solvent acceptor number (AN)and the linear solvation energy relationships (LSER), respectively, with the Raman shifts of carbonyl group. There is little linear relation between dielectric constants and the Raman shift. These solvents were divided into two sections by the acceptor number. The two sections exhibit a good correlation with AN, respectively. These frequencies show a better correlation with LSER than the solvent AN. How the solvents interacts with the C==O can be obtained from the regression coefficients.
ABSTRACT
Fermi resonance is one of the general and important phenomena in vibration spectra. The method of solvent variation is one of the main methods to study Fermi resonance. In the present paper, FTIR spectroscopy was used to study the Fermi resonance of p-benzoquinone in thirteen solvents. The results show that there are some function relationships between the dielectric constant of solvent and the intensity ratio of Fermi resonance. And the empirical formula was obtained by curve fitting. The equation of Kirkwood-Bauer-Magat was applied to the study of Fermi resonance. And the authors obtained the relation between the intensity ratio R and the dielectric constant epsilon. This result is in accordance with the empirical formula. In order to confirm our result, the infrared data of R. A. Nyquist and J. K. Seehra were analyzed. These results are in accord with that of p-benzoquinone.
ABSTRACT
According to the wavelet multi-resolution analysis, the optical spectrum signal received by CCD was processed and analyzed by using the wavelet transformation technique. The noise in the optical spectrum signal can be removed by using the wavelet multi-resolution analysis technique. The curve of spectral signal can be smoothed. The ratio of signal to noise was enhanced. The spectrum of Asource by CCD was smoothed with wavelet multi-resolution analysis. The processing results with different wavelets in different orders were discussed. An effective data processing method was used for spectrum analysis. The difficulty in the analysis and processing of real-time signal can be solved, which is significant in the color testing field.
