The intermolecular relaxation of the NH stretching vibration of pyrrole in the liquid phase: a two-mode dynamical study

The mechanism for intermolecular relaxation of the NH stretching vibration of pyrrole in the liquid phase is explained by a classical two-mode (NH stretch, ring mode of the neighboring molecule) model, which implies a 3-1 Fermi resonance between the Morse stretch and the harmonic ring vibrations, coupled by a hydrogen bond interaction. The phase space structure, energy flow and population decay obtained with this model give a qualitative and semi-quantitative explanation of the relaxation pathways and decay time of the excited NH stretch.