Bottlenecks to vibrational energy flow in OCS: Structures and mechanisms

TL;DR

This paper investigates the phase space bottlenecks causing slow and uneven vibrational energy flow in OCS, revealing the role of invariant tori and elliptic periodic orbits in energy relaxation dynamics.

Contribution

It identifies specific phase space structures, namely invariant tori around elliptic orbits, as the bottlenecks affecting vibrational energy transfer in OCS.

Findings

Identification of phase space bottlenecks in OCS.

Relation of trapping mechanisms to stability of invariant tori.

Explanation of nonstatistical energy relaxation behavior.

Abstract

Finding the causes for the nonstatistical vibrational energy relaxation in the planar carbonyl sulfide (OCS) molecule is a longstanding problem in chemical physics: Not only is the relaxation incomplete long past the predicted statistical relaxation time, but it also consists of a sequence of abrupt transitions between long-lived regions of localized energy modes. We report on the phase space bottlenecks responsible for this slow and uneven vibrational energy flow in this Hamiltonian system with three degrees of freedom. They belong to a particular class of two-dimensional invariant tori which are organized around elliptic periodic orbits. We relate the trapping and transition mechanisms with the linear stability of these structures.