Formation of H3+ from ethane dication induced by electron impact

Yu Zhang,Wandong Yu,Yaming Zou,Li Chen,Chuan-Lu Yang,Long Wei,Enliang Wang,Yueying Qi,Bo Wang,Jie Han,Baihui Ren,Baoren Wei

doi:10.1038/s42004-020-00415-9

Abstract

Hydrogen migration plays an important role in the chemistry of hydrocarbons which considerably influences their chemical functions. The migration of one or more hydrogen atoms occurring in hydrocarbon cations has an opportunity to produce the simplest polyatomic molecule, i.e. H3+. Here we present a combined experimental and theoretical study of H3+ formation dynamics from ethane dication. The experiment is performed by 300 eV electron impact ionization of ethane and a pronounced yield of H3+ + C2H3+ coincidence channel is observed. The quantum chemistry calculations show that the H3+ formation channel can be opened on the ground-state potential energy surface of ethane dication via transition state and roaming mechanisms. The ab initio molecular dynamics simulation shows that the H3+ can be generated in a wide time range from 70 to 500 fs. Qualitatively, the trajectories of the fast dissociation follow the intrinsic reaction coordinate predicted by the conventional transition state theory. The roaming mechanism, compared to the transition state, occurs within a much longer timescale accompanied by nuclear motion of larger amplitude.

Highlights

Hydrogen migration plays an important role in the chemistry of hydrocarbons which considerably influences their chemical functions
Due to the close connection to the potential energy surface (PES) of dication states, the kinetic energy release (KER) can serve as a mechanistic probe through comparing with the reverse activation energy of the reaction path obtained by the transition state (TS) calculation
On the other hand, employing the time-resolved pump-probe technique and combining high-level ab initio molecular dynamics (AIMD) simulations[12,13,14,15], direct access has been provided to the H3+ formation dynamics and another route to H3+ formation has been proposed

Summary

Introduction

Hydrogen migration plays an important role in the chemistry of hydrocarbons which considerably influences their chemical functions. The structural evolution of the dications showed that H3+ ions were formed through a roaming mechanism involving an H2 molecule.

Results

Conclusion