X-ray Induced Ultrafast Electron and Fragmentation Dynamics in Heavy-element Containing Molecules

Characterization of the inner-shell decay processes in heavy element containing molecules is key to understand x-ray damage of molecules and materials and realize medical applications with Auger-emitting radionuclides. The Advanced Photon Source provides intense, tunable, narrow bandwidth x-ray beams that are well suited to studies of x-ray absorption and core-hole decay processes in systems containing heavy elements. The 1s hole states in the heavy elements largely decay by x-ray emission and are followed by additional Auger decays that increase the ion's charge state until the final state is reached. Using the x-ray/ion coincidence method, we recorded ion time-of-flight data with a multi-hit, position-sensitive detector for Br2, IBr, CH2IBr, and CF3Br following x-ray absorption at the Br and I K-edges. We present the charge states and kinetic energies of two or more correlated fragment ions associated with core-excited states produced during the various steps of the cascades. To understand the dynamics leading to the ion data, we develop a computational model that combines Monte-Carlo/Molecular Dynamics simulations with a classical over-the-barrier model to track inner-shell cascades and redistribution of electrons in valence orbitals and nuclear motion of fragments.