Influence of low frequency modes on dynamical concertedness in double proton transfer dynamics

TL;DR

This paper investigates how low frequency modes influence the reaction pathways in double proton transfer by analyzing phase space dynamics and employing Lagrangian descriptors to identify key manifolds.

Contribution

It introduces a phase space analysis of a three degree of freedom model, highlighting the impact of transverse modes on reaction mechanisms and pathway classification.

Findings

Low frequency transverse modes significantly affect reaction pathways.

Lagrangian descriptors effectively identify phase space manifolds related to reaction pathways.

Delay time distributions correlate with phase space structures for reaction mechanism insights.

Abstract

We analyze the classical phase space dynamics of a three degree of freedom Hamiltonian that models multiple bond breaking and forming reactions. The model Hamiltonian, inspired from studies on double proton transfer reactions, allows for exploring the dynamical consequences of higher index saddles on multidimensional potential energy surfaces. Studies have shown that coupling of low frequency transverse modes to the reaction coordinate can significantly influence the reaction mechanism, concerted or sequential, as inferred from a reduced dimensional analysis. Using the notion of dynamically concerted and sequential pathways, we provide insights into the role of the transverse modes by studying the delay times between the formation of two bonds. The delay time distribution, used extensively in earlier studies, is placed on a firm dynamical footing by correlating it with the phase space manifolds, determined using the technique of Lagrangian descriptors. We establish the utility of Lagrangian descriptors in identifying the phase space manifolds responsible for the dynamically concerted and dynamically sequential pathways.