Time-domain calculations of the polarized Raman and two-dimensional infrared spectra of liquid N,N-dimethylformamide

A time-domain method for calculating polarized Raman and two-dimensional infrared (2D-IR) spectra that includes the effects of both the diagonal frequency modulations (of individual molecules in the system) and the off-diagonal (intermolecular) vibrational coupling is presented. It is then applied to the case of the amide I band of liquid N,N-dimethylformamide. The non-coincidence effect in the polarized Raman spectrum and the corresponding spectral feature in the 2D-IR spectrum related to the off-diagonal vibrational coupling and delocalization of vibrational modes are discussed.