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摘要
Traditionally, the Raman spectrum of ethanol in the C-H vibrational stretching region between 2800 cm(-1) and 3100 cm(-1) had been assigned as three bands of the -CH2 symmetric stretching, the -CH3 symmetric stretching, and the -CH3 antisymmetric stretching. In this report, new Raman spectral features were observed for ethanol and two deuterated ethanols, that is, CD3CH2OH and CH3CD2OH, in both gaseous and liquid phases with polarized photoacoustic Raman spectroscopy (PARS) as well as normal Raman spectroscopy. With the aid of depolarization ratio measurements and quantum chemical calculations, different assignments were presented to the complex spectral features in the ethanol Raman spectra. In the gaseous ethanol spectra, the band at similar to 2882 cm(-1) was assigned to the overlapping symmetric stretching vibrational modes of both -CH2 and -CH3; the band at similar to 2938 cm(-1) was assigned to the two symmetric -CH3 Fermi resonance modes and the weak -CH2 antisymmetric stretching mode; and the band at similar to 2983 cm(-1) was assigned to the symmetric -CH2 Fermi resonance mode and the weak -CH3 antisymmetric stretching mode. The liquid ethanol spectral features are similar to the gaseous spectra with a much stronger -CH3 antisymmetric stretching mode and a red shift of about 10 cm(-1), which can be attributed to the effects of solvent interactions. The new assignments of both the gaseous and liquid ethanol spectra not only confirmed the recent results from the sum-frequency generation vibrational spectroscopy studies of the ethanol molecules at the air/liquid interface but the differences in the gaseous and liquid phases, as well as at the interfaces, can also provide detailed experimental evidence in understanding of the molecular interactions and dynamics of the ethanol molecule in different chemical environments.
- 出版日期2007-6-28
- 单位中国科学技术大学
