Classical and quantum dynamical manifestations of index-2 saddles:
concerted versus sequential reaction mechanisms
- URL: http://arxiv.org/abs/2009.07716v1
- Date: Wed, 16 Sep 2020 14:39:20 GMT
- Title: Classical and quantum dynamical manifestations of index-2 saddles:
concerted versus sequential reaction mechanisms
- Authors: Priyanka Pandey, Shibabrat Naik and Srihari Keshavamurthy
- Abstract summary: We study the presence of higher index saddles on a multidimensional potential energy surface.
We show that the ultrafast shift of the mechanism from a concerted to a stepwise one is essentially a classical dynamical effect.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: The presence of higher index saddles on a multidimensional potential energy
surface is usually assumed to be of little significance in chemical reaction
dynamics. Such a viewpoint requires careful reconsideration, thanks to elegant
experiments and novel theoretical approaches that have come about in recent
years. In this work, we perform a detailed classical and quantum dynamical
study of a model two degree of freedom Hamiltonian, which captures the essence
of the debate regarding the dominance of a concerted or a stepwise reaction
mechanism. We show that the ultrafast shift of the mechanism from a concerted
to a stepwise one is essentially a classical dynamical effect. In addition, due
to the classical phase space being a mixture of regular and chaotic dynamics,
it is possible to have a rich variety of dynamical behaviour, including a
Murrell-Laidler type of mechanism, even at energies sufficiently above that of
the index-2 saddle. We rationalize the dynamical results using an explicit
construction of the classical invariant manifolds in the phase space.
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