Two-dimensional correlation infrared spectroscopic study of N-methylacetamide as a function of temperature

Generalized two-dimensional (2D) correlation vibrational spectroscopy has been used to study N-methylacetamide (NMA) as a function of temperature. It has been found that all the major bands of NMA are shifted in frequency as the temperature is raised. This gives rise to the appearance of new features in the 2D plots. These new features are not true bands, because they are not fundamental normal modes of vibration, but correspond to difference bands used to generate the correlation plots. Analysis of the amide I region of the spectrum suggests that transition dipole coupling plays a key role in the splitting of the amide I band in the liquid state.