New C-H Stretching Vibrational Spectral Features in the Raman Spectra of Gaseous and Liquid Ethanol †

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 ∼2882 cm-1 was assigned to the overlapping symmetric stretching vibrational modes of both −CH2 and −CH3; the band at ∼2938 cm-1 was assigned to the two symmetric −CH3 Fermi resonance modes and the weak −CH2 antisymmetric stretching mode; and the band at ∼2983 cm-1 was assigned ...

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