Multiple charge transfer driven complex reaction dynamics: covalent bonding meets van der Waals interactions

TL;DR

This study uses advanced spectroscopic techniques and ab initio calculations to unravel ultrafast, multi-step charge transfer processes and nonadiabatic reaction pathways in a covalently bonded N2Ar dimer, revealing complex electron dynamics.

Contribution

It provides the first detailed step-by-step tracking of multiple charge transfer events and structural evolution in a simple covalent-van der Waals dimer, combining experimental and theoretical methods.

Findings

Sequential charge transfer events trigger complex reaction pathways.

Structural evolution influences multiple charge transfer processes.

Nonadiabatic transitions involving conical intersections are key to dynamics.

Abstract

Ultrafast charge transfer (CT) processes redistribute electronic charge within and between molecular units and play a central role in many physical, chemical, and biological phenomena. However, the microscopic pathways of multiple CT events, including the coupled structural evolution and energy redistribution, are challenging to disentangle experimentally in complex systems. To obtain controlled insight into such dynamics, well-defined properties are required. Here, we investigate the N2Ar dimer, which combines a covalent bond with a weak van der Waals interaction, using site-selective synchrotron photoionization and coincident detection of electrons and ions. Combined with ab initio calculations, this approach enables step-by-step tracking of ultrafast CT and fragmentation dynamics. We find that the dimer's structural evolution triggers a second CT event, opening complex reaction pathways in which electrons are transferred back and forth between Ar and N2, through two nonadiabatic transitions involving conical intersections. These results demonstrate that sequential multiple CT-induced transitions, even in a simple dimer, provide controlled insight into nonadiabatic reaction mechanisms relevant to complex systems.