Reconstructing real-space geometries of polyatomic molecules undergoing strong field laser-induced Coulomb explosion

Coulomb explosion is an established momentum imaging technique, where the molecules are ionized multiple times on a femtosecond time scale before breaking up into ionized fragments. By measuring the momentum of all the ions, information about the initial molecular structure is theoretically available. However, significant geometric changes due to multiple ionizations occur before the explosion, posing a challenge in retrieving the ground-state structure of molecules from the measured momentum values of the fragments. In this work, we investigate theoretically and experimentally such a connection between the ground-state geometry of a polyatomic molecule (OCS) and the detected momenta of ionic fragments from the Coulomb explosion. By relying on time-dependent density functional theory (TDDFT), we can rigorously model the ionization dynamics of the molecule in the tunneling regime. We reproduce the energy release and the Newton plot momentum patterns of an experiment in which OCS is ionized to the 6+ charge state. Our results provide insight into the behavior of molecules during strong field multiple ionization, opening a way toward precision imaging of real-space molecular geometries using tabletop lasers. Understanding molecular structure and dynamics through strong-field laser interactions holds great promise. The authors use quantum calculations to show how bonds and angles evolve in an OCS molecule ionized six times by a 7 fs, 800 nm laser pulse, accurately predicting our experimental results.