Influence of vibrational frequency mismatch on phase-space bottlenecks to intramolecular energy redistribution and molecular fragmentation

Abstract

We report studies of classical models of unimolecular fragmentation of van der Waals complexes using the methodologies of Hamiltonian mappings and flows. The effect of frequency mismatch between harmonic molecular vibrations of a host molecule and the van der Waals bond-stretching motion is shown to dominate vibrational energy redistribution and fragmentation. Our results show that a crossover exists when the frequency mismatch is increased from a stochastic regime of resonances between the nonlinear oscillators to a regular regime where the system behaves like an integrable system. Our model systems include both collinear and T-shaped oscillator displacement configurations, as well as a many-oscillator system that included both classes of motions. Oscillator parameter ranges were used that approximate vibrations in C6H6⋅He and C6H6⋅Ar van der Waals complexes.