Shuqin Gao

Study of high-pressure Raman intensity behavior of aromatic hydrocarbons: Benzene, biphenyl and naphthalene☆

Raman spectra of benzene, naphthalene and biphenyl have been taken up to a pressure of 13 GPa. The results for benzene and naphthalene indicate that the perturbation of inter-molecular π-π stacking effect on the Raman intensity is neglectable. For biphenyl, all the Raman peaks show intensity enhancement during the compression process, which indicates the planar intra-molecular aromatic conformation play an important role in the intensity increments of Raman bands. For three aromatic compounds, C-H stretching vibration bands located at about 3000 cm(-1) show intriguing intensity changes during compression account for the inter-molecular C-H⋯π interaction.

The effect of the Fermi resonance on the Raman scattering cross sections of the Fermi doublet ν1 and 2ν2 of liquid carbon disulfide in benzene.

The effect of the Fermi resonance (FR) on the Raman scattering cross sections (RSCSs) of the Fermi doublet ν1, 2ν2 of liquid CS2 in C6H6 using the method of changing the volume concentration of the solution is investigated. We have calculated the RSCSs of the Fermi doublet ν1, 2ν2 using Onsagers theory with the 992 cm(-1) Raman line of C6H6 as the internal standard. The result shows that the RSCS of the ν1 line decreases with decreasing the volume concentration of CS2, while that of the 2ν2 line unexpectedly increases. With decreasing the volume concentration of CS2, two main effects of the solvent effect (SE) and the FR in binary solution that can make the ν1, 2ν2 RSCSs change: the SE, as calculated, reduces both the ν1 and 2ν2 RSCSs; the FR plays a significant role in reducing the ν1 RSCS and enhancing the 2ν2 RSCS. In comparison with our previous investigation [J. Raman Spectrosc. 41 (2010) 776-779], it was found that the stronger the FR is, the more the RSCS of the ν1 decreases and the 2ν2 increases. Thus, we proposed that the result can be best explained by taking into account the effect of the FR on the RSCSs of the Fermi doublet. In addition, this paper also gives an explanation to the experimental results deviating from the theoretical results of the scattering coefficients of CS2 in solvent C6H6 as mentioned in Finis paper.

Study on Raman spectrum intensity depending on temperature with optical-fiber method

Abstract The Raman spectrum intensity of CCl4 is measured in the temperature range from 0°C to 65.0°C with the optical-fiber A maximum value exists when it alters with a variety of temperatures. Several main factors influencing the Raman spectrum intensity in an optical fiber are calculated. Theorical and experimental results are in agreement.

Raman spectroscopy study on the ν1-2ν2 Fermi resonance of liquid carbon disulfide in binary solutions: Effect of the weak hydrogen bond formation on the Fermi resonance

We have measured the Raman spectra of liquid CS(2) at different volume concentrations in CHCl(3) and CH(2)Cl(2) solutions. With decreasing the volume concentration of CS(2), a noticeable growth in the 2ν(2) band frequency was observed, while the ν(1) band location remained practically unchanged. This asymmetric wavenumber shift phenomenon of the Fermi doublet ν(1) and 2ν(2) of CS(2) has been ascribed to weak, non-conventional hydrogen bonds formed between the CS(2) and the solvent molecules. These weak hydrogen bonds were also responsible for significant decreases in the C-H bond symmetric stretching vibration band frequencies of CHCl(3) and CH(2)Cl(2). The values of the ν(1)-2ν(2) FR parameters of CS(2) in CH(2)Cl(2) and CHCl(3) at different volume concentrations were calculated according to the FR theory. The magnitude of the FR coupling coefficient W of CS(2) increases upon dilution with CH(2)Cl(2) and CHCl(3), indicating that the vibrational anharmonicity is relatively sensitive to variations in the weak hydrogen bonding. Compared with the changing tendencies of Fermi coupling coefficient W of CS(2) in CH(2)Cl(2) and CHCl(3) at different volume concentrations, we discussed the effect of the weak hydrogen bond formation on the FR and the asymmetric wavenumber shift phenomenon of the Fermi doublet ν(1) and 2ν(2) of CS(2).