Abstract
A model of the HNC/HCN isomerization reaction with three vibrational degrees of freedom is studied. The semiclassical technique of adiabatic switching is used to obtain quantizing trajectories in the metastable HNC potential well. Adjustment of these eigenvalues to account for the degenerate bend mode not included in our model gives agreement to within 20 cm−1 of the quantum results. Isomerization data show that this system has a high degree of mode specificity. Fourier transform analysis of the vibrational motion identifies two pathways for energy transfer. One pathway occurs at high bending quantum numbers and is believed to involve potential features and chaotic motion at high bending angle. The second pathway is a classical resonance in which the sum of the CN stretching frequency and twice the bending frequency is equal to the H atom stretching frequency. The resonance acts to transfer energy into the bending mode which allows the trajectory to reach the high bending angle region of the potential where the first mechanism can cause isomerization. It is determined that the role of the CN mode is to allow for enhanced stretch–bend coupling through a three mode resonance. This study concludes that bending degrees of freedom play a major role in intramolecular energy transfer dynamics in agreement with the results of previous studies.
Published Version
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