Аннотация:
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 behavior, including a
Murrell – Laidler type 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.
Priyanka Pandey is supported by a graduate fellowship from IIT Kanpur; Srihari Keshavamurthy’s
research is supported by the Science and Engineering Research Board (SERB) India
(project no. EMR/006246). Shibabrat Naik acknowledges the support of EPSRC Grant
No. EP/P021123/1.
Поступила в редакцию: 10.09.2020 Принята в печать: 28.10.2020
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Komal Yadav, Renuka Pradhan, Upakarasamy Lourderaj, “Influence of second-order saddles on reaction mechanisms”, Faraday Discuss., 238 (2022), 183
Priyanka Pandey, Srihari Keshavamurthy, “Dynamic matching—Revisiting the Carpenter model”, J of Physical Organic Chem, 35:11 (2022)
Priyanka Pandey, Shibabrat Naik, Srihari Keshavamurthy, “Influence of low frequency modes on dynamical concertedness in double proton transfer dynamics”, Communications in Nonlinear Science and Numerical Simulation, 109 (2022), 106326