Algebraic description of n-alkane molecules: first overtone of CH stretching modes

The one-dimensional algebraic model is applied to analyze infrared spectra of n-alkane molecules. We consider CH stretching vibrations in both fundamental (v = 1) and first overtone (v = 2) energy regions. We show that a relatively small set of well-defined parameters leads to a very good agreement with observed data. Both CH2 and CH3 vibrations are accounted for. In particular, we suggest that first overtone infrared spectra can be fairly well described without adding complex anharmonic (Fermi) interactions. Their inclusion is required however to obtain a closer agreement with the available experimental spectra.