The quantum dynamic flow of cncrg out of an inithll~ cscitcd CH bond in LI model hydrocarbon is calculated numerically. The results are interpreted in terms of a state-to-state flow of probability and contrasted to clsssiwl trajjecroc enscmble aver;~ges. We show that quantum energy flow has a direct classical interpretation in terms of sequential non-linear resonances. We also present evidence for and the mechanism of significant short-time non-classical effects in the quantum cncrzy flow. l_ Introduction Considerable theoretical study has been devoted 10 intramolecular energy flow and relaxation of vibntionally excited initial states. These studies have generally employed either a time-dependent classical trajectory analysis [l--7] or a time-independent quantum mechanical analysis [8-l I]_ In this letter, we describe a numerical calculation of the time-dependent quantum dynamics of molecular vibrations, with analysis of the energy flow, out of an excited terminal CH bond in a model hydrocarbon chain with many degrees of freedom.
We have established elsewhere that classical intramolecular vibrational energy flow in chains may be clearly understood in terms of a classical picture of non-linear resonances amongst zero-order modes of motion in the molecule [l] _ While classical trajectory studies are valuable tools in interpreting vibrational dynamics, they are not definitive concerning energy flow in a quantum world. In this letter, we will find that in the model hydrocarbon chain, there are important differences between classical and quantum