Vibration study of the chain conformation of the n-nonane with one gauche conformation

Ab initio calculations were used to calculate normal mode frequencies and intensities of four stable conformations of n-nonane including all-trans and other three conformations with one gauche. The overall frequency region including IR and Raman spectra was analyzed to get the full spectra information of n-nonane, and to explore the relation between frequency and disorder in the overall frequency region. The bands in the IR spectra and in the Raman spectra were found to be associated with specific conformations, and therefore the character bands of each conformation could be obtained. For the bands with the same vibration modes, the trend with the change of conformation was also discussed which played an important role in the experiments.