Differentiating Three-Dimensional Molecular Structures using Laser-induced Coulomb Explosion Imaging

TL;DR

This paper demonstrates that laser-induced Coulomb explosion imaging can differentiate 3D molecular structures, including nonplanar organic molecules, providing a promising tool for tracking ultrafast structural changes in chemical reactions.

Contribution

It extends CEI techniques to 3D structures using tabletop lasers and shows that distinct fragmentation patterns reveal molecular geometries.

Findings

Distinctive 3D fragment-ion patterns for different molecules

Classical simulations qualitatively reproduce experimental patterns

Potential for real-time tracking of molecular structural changes

Abstract

Coulomb explosion imaging (CEI) with x-ray free electron lasers has recently been shown to be a powerful method for obtaining detailed structural information of gas-phase planar ring molecules [R. Boll et al. Nat. Phys. 18, 423-428 (2022)]. In this Letter, we investigate the potential of CEI driven by a tabletop laser and extend this approach to differentiating three-dimensional (3D) structures. We study the static CEI patterns of planar and nonplanar organic molecules that resemble the structures of typical products formed in ring-opening reactions. Our results reveal that each molecule exhibits a well-localized and distinctive pattern in 3D fragment-ion momentum space. We find that these patterns yield direct information about the molecular structures and can be qualitatively reproduced using a classical Coulomb explosion simulation. Our findings suggest that laser-induced CEI can serve as a robust method for differentiating molecular structures of organic ring and chain molecules. As such, it holds great promise as a method for following ultrafast structural changes, e.g., during ring-opening reactions, by tracking the motion of individual atoms in pump-probe experiments.