Nonstatistical dynamics on the caldera

Peter Collins

doi:10.1063/1.4889780

Nonstatistical dynamics on the caldera

2014-07-17

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DOI：10.1063/1.4889780

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We explore both classical and quantum dynamics of a model potential exhibiting a caldera: that is, a shallow potential well with two pairs of symmetry related index one saddles associated with entrance/exit channels. Classical trajectory simulations at several different energies confirm the existence of the dynamical matching phenomenon originally proposed by Carpenter, where the momentum direction associated with an incoming trajectory initiated at a high energy saddle point determines to a considerable extent the outcome of the reaction (passage through the diametrically opposing exit channel). By studying a stretched version of the caldera model, we have uncovered a generalized dynamical matching: bundles of trajectories can reflect off a hard potential wall so as to end up exiting predominantly through the transition state opposite the reflection point. We also investigate the effects of dissipation on the classical dynamics. In addition to classical trajectory studies, we examine the dynamics of quantum wave packets on the caldera potential (stretched and unstretched). These computations reveal a quantum mechanical analogue of the dynamical matching phenomenon, where the initial expectation value of the momentum direction for the wave packet determines the exit channel through which most of the probability density passes to product. (C) 2014 AIP Publishing LLC.

Keywords:

QUANTUM ENERGY-FLOW

THERMAL UNIMOLECULAR VINYLCYCLOPROPANE

TRANSITION-STATE THEORY

PHASE-SPACE

CHEMICAL-REACTIONS

REACTIVE SCATTERING

REACTION PATHWAY

SIMULATIONS

MECHANISM

STEREOCHEMISTRY

Nonstatistical dynamics on the caldera

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