Revisiting roaming trajectories in ketene isomerization at higher dimensionality
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Roaming dynamics have been observed in a three-dimensional model of the ketene isomerization reaction. The roaming trajectories sample the region between the outer potential barriers closest to the respective ketene isomers and involve turning points along the reaction coordinate in a polar representation. These roaming trajectories avoid the intrinsic reaction coordinate and the intermediates to which it is associated. Thus, one-dimensional transition state theory (TST) is generally insufficient as has been confirmed through an analysis of the reactive flux along the dividing surface (DS). A global representation of the DS, however, leads to accurate TST rate constants. The exact and TST microcanonical rates of isomerization have been obtained for the three-dimensional model and compare well to experiment. The global DS is therefore particularly important for obtaining rates in reactions that exhibit roaming. This work thus confirms the findings of our previous two-dimensional treatment of ketene isomerization (Ulusoy et al. in J. Phys. Chem. A 117:7553–7560, 2013).
KeywordsTransition state theory Roaming Reaction dynamics Classical trajectories Reaction rate Theory
It a pleasure to publish this article in honor of Greg Ezra. This work has been partially supported by the Air Force Office of Scientific Research through Grant No. FA9550-12-1-0483. I. U. acknowledges the Alexander von Humboldt Foundation, Germany, for support through a Feodor Lynen Fellowship. This work used the HPC resources (Stampede) at the Texas Advanced Computing Center (TACC) at the University of Texas at Austin through XSEDE allocation under award No. TG-CTS090079. We are also grateful to Prof. J. Daniel Gezelter for discussions  about the energetics and masses associated with the ketene surface.
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