Imaging Chemical Transformations with Ultrafast X-ray Lasers
Kelly J. Gaffney
The complex coupled motion of electrons and nuclei govern the chemical transformations of molecules. While ultrafast optical lasers have long been able to capture ultrafast chemical reaction dynamics, interpretation has often proved ambiguous. The advent of ultrafast x-ray lasers provides a novel approach to imaging chemical dynamics with unprecedented spatial and temporal resolution. I will present mechanistic studies of the back electron transfer and intersystem crossing dynamics that occur following electronic excitation in iron-based transition metal complexes, including iron-carbene photosensitizers and the metalloprotein cytochrome C. These experiments have combined the simultaneous measurement of hard x-ray emission spectroscopy (XES) to track the charge and spin dynamics of the metal site with x-ray solution scattering (XSS) to characterize changes in the intramolecular metal-ligand bonding. We intend to use the mechanistic understanding extracted from these measurements to inform the design of transition metal complexes for photosensitizer and photocatalysis applications.