The phase space geometry underlying roaming reaction dynamics

Abstract

Recent studies have found an unusual way of dissociation in formaldehyde. It can be characterized by a hydrogen atom that separates from the molecule, but instead of dissociating immediately it roams around the molecule for a considerable amount of time and extracts another hydrogen atom from the molecule prior to dissociation. This phenomenon has been coined roaming and has since been reported in the dissociation of a number of other molecules. In this paper we investigate roaming in Chesnavich's CH${}_4^{+}$ model. During dissociation the free hydrogen must pass through three phase space bottleneck for the classical motion, that can be shown to exist due to unstable periodic orbits. None of these orbits is associated with saddle points of the potential energy surface and hence related to transition states in the usual sense. We explain how the intricate phase space geometry influences the shape and intersections of invariant manifolds that form separatrices, and establish the impact of these phase space structures on residence times and rotation numbers. Ultimately we use this knowledge to attribute the roaming phenomenon to particular heteroclinic intersections.

References in corpus (8)

• Thirty Years of Turnstiles and Transport
• Microcanonical rates, gap times, and phase space dividing surfaces
• Multiple Transition States and Roaming in Ion-Molecule Reactions: a Phase Space Perspective
• Roaming dynamics in ion-molecule reactions: phase space reaction pathways and geometrical interpretation
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Cited by in corpus (10)

• Geometry of transit orbits in the periodically-perturbed restricted three-body problem
• Phase-space resolved rates in driven multidimensional chemical reactions
• Using Lagrangian descriptors to uncover invariant structures in Chesnavich's Isokinetic Model with application to roaming
• Isodrastic Magnetic fields for suppressing transitions in guiding-centre motion
• Roaming at Constant Kinetic Energy: Chesnavich's Model and the Hamiltonian Isokinetic Thermostat
• Influence of mass and potential energy surface geometry on roaming in Chesnavich's CH${}_4^{+}$ model
• Controlling reaction dynamics in chemical model systems through external driving
• Predicting trajectory behaviour via machine-learned invariant manifolds
• Phase space structures causing the reaction rate decrease in the collinear hydrogen exchange reaction
• Roaming in acetaldehyde