Distinguishing Molecular Structures using Laser-induced Coulomb Explosion Imaging

Recently, Coulomb explosion imaging (CEI) with both XFELs and near-infrared (NIR) femtosecond lasers was shown to be a powerful method to obtain detailed structural information of gas-phase molecules with ten or more atoms. This suggests that time-resolved CEI could be used to follow the structural dynamics of molecules in chemical reactions such as ring opening. A ring-opening reaction can lead to a variety of final products, some of which are non-planar and have low symmetry (e.g., chain structures and smaller rings with higher ring strain). In this work, we investigate the static CEI patterns of a series of molecules that resemble the structures of "open-ring" and "closed-ring" products formed in a UV-induced ring-opening reaction. These patterns can be used as reference images to help identify the photoproducts in time-resolved CEI experiments. The experimental data are compared with CEI patterns produced from classical Coulomb explosion simulations to shed light on different aspects of the problem and to discuss the potential of distinguishing different products in ring-opening reactions using this method.