When
Presenter:
Dr. Kelly Gaffney
Professor, Photon Science SLAC National Accelerator Laboratory, Stanford University
Abstract:
The efficient and directed use of light for chemical applications requires directing the electronic and nuclear motion of molecules on electronic excited states toward the desired chemical outcomes. 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-carbene based photosensitizers. 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.
Biosketch:
Professor Gaffney leads a research team focused on femtosecond resolution measurements of chemical dynamics in complex condensed phase systems. This research takes advantage of recent advances in ultrafast x-ray lasers, like the LCLS at SLAC National Accelerator Laboratory, to directly observe chemical reactions on the natural time and length scales of the chemical bond – femtoseconds and Ångströms. This research focuses on the discovery of design principles for controlling the non-equilibrium dynamics of electronic excited states and using these principles to spark new approaches to light-driven catalysis in chemical synthesis.
This research builds on Professor Gaffney’s extensive experience with ultrafast optical laser science and technology. This work began with time- and angle- resolved two photon photoemission studies of electron solvation and localization at interfaces as a graduate student working with Professor Charles Harris at the University of California at Berkeley and extended to multidimensional vibrational spectroscopy studies of hydrogen bonding and ion solvation dynamics in solution during postdoctoral studies with Professor Michael Fayer at Stanford and as an Assistant Professor. The transition to ultrafast x-ray science began in 2004 at SLAC, where he helped establish the first chemical dynamics research program at SLAC.