Intramolecular vibrational energy redistribution and the quantum ergodicity transition: a phase space perspective

Intramolecular vibrational energy redistribution (IVR) impacts the dynamics of reactions in a profound way. Theoretical and experimental studies are increasingly indicating that accounting for the finite rate of energy flow is critical for uncovering the correct reaction mechanisms and calculating a...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2020-05, Vol.22 (2), p.11139-11173
Main Authors: Karmakar, Sourav, Keshavamurthy, Srihari
Format: Article
Language:English
Subjects:
Anharmonicity
Coupling (molecular)
Degrees of freedom
Dimensional analysis
Dynamical systems
Energy flow
Ergodic processes
Matrix theory
Nonlinear analysis
Nonlinear dynamics
Phase transitions
Reaction mechanisms
System effectiveness
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Summary:Intramolecular vibrational energy redistribution (IVR) impacts the dynamics of reactions in a profound way. Theoretical and experimental studies are increasingly indicating that accounting for the finite rate of energy flow is critical for uncovering the correct reaction mechanisms and calculating accurate rates. This requires an explicit understanding of the influence and interplay of the various anharmonic (Fermi) resonances that lead to the coupling of the vibrational modes. In this regard, the local random matrix theory (LRMT) and the related Bose-statistics triangle rule (BSTR) model have emerged as powerful and predictive quantum theories for IVR. In this Perspective we highlight the close correspondence between LRMT and the classical phase space perspective on IVR, primarily using model Hamiltonians with three degrees of freedom. Our purpose for this is threefold. First, this clearly brings out the extent to which IVR pathways are essentially classical, and hence crucial towards attempts to control IVR. Second, given that LRMT and BSTR are designed to be applicable for large molecules, the exquisite correspondence observed even for small molecules allows for insights into the quantum ergodicity transition. Third, we showcase the power of modern nonlinear dynamics methods in analysing high dimensional phase spaces, thereby extending the deep insights into IVR that were earlier gained for systems with effectively two degrees of freedom. We begin with a brief overview of recent examples where IVR plays an important role and conclude by mentioning the outstanding problems and the potential connections to issues of interest in other fields. The onset of facile intramolecular vibrational energy flow can be related to features in the connected network of anharmonic resonances in the classical phase space.
ISSN:1463-9076
1463-9084
DOI:10.1039/d0cp01413c