Intramolecular vibrational energy flow in model four-atom systems

Abstract

Intramolecular energy transfer from local bond modes is studied by using quasiclassical trajectories. The energy in a local mode as a function of time is computed to determine the nature and time scale for the decay of local mode excitation. Variations of four basic models are examined: HCCC, HOOH, HNNH, and HC ≡ CH. Potential-energy surfaces for the models are sums of Morse functions for bond stretches and harmonic bending functions. The potential for HOOH torsional motion is represented by a truncated Fourier cosine series. The emphasis of the study is on H2O2. The decay of OH overtone excitation is characterized by slow, irreversible flow of energy out of the OH as a function of time. The rate of energy transfer is strongly dependent upon the OOH bending and the torsional motions.