Quantum simulations of nonlinear resonance and torsional dynamics

A simple model of the vibrational dynamics of ABBA type sequentially bonded tetra-atomic molecules is investigated by quantum mechanical methods. The model Hamiltonian excludes bond stretching and asymmetric bending but includes the kinematic coupling between the torsional motion and symmetric bond bending which results in nonlinear resonances. The effect of this coupling on energy levels and the timescale of intramolecular energy transfer is evaluated and discussed in terms of both resonant and nonresonant effects.