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.
van Driel, T. B., Kjaer, K. S., Hartsock, R. W., Dohn, A. O., Harlang, T., Chollet, M., … Gaffney, K. J. (2016). Atomistic characterization of the active-site solvation dynamics of a model photocatalyst. NATURE COMMUNICATIONS, 7.
Kunnus, K., Li, L., Titus, C., Lee, S. J., Reinhard, M. E., Koroidov, S., … Gaffney, K. J. (2020). Chemical control of competing electron transfer pathways in iron tetracyano-polypyridyl photosensitizers. CHEMICAL SCIENCE, 11(17), 4360–73.
Lemke, H. T., Kjaer, K. S., Hartsock, R., van Driel, T. B., Chollet, M., Glownia, J. M., … Cammarata, M. (2017). Coherent structural trapping through wave packet dispersion during photoinduced spin state switching. NATURE COMMUNICATIONS, 8.
Jha, S. K., Ji, M., Gaffney, K. J., & Boxer, S. G. (2011). Direct measurement of the protein response to an electrostatic perturbation that mimics the catalytic cycle in ketosteroid isomerase. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 108(40), 16612–17.
Kjar, K. S., Van Driel, T. B., Harlang, T. C., Kunnus, K., Biasin, E., Ledbetter, K., … Gaffney, K. J. (2019). Finding intersections between electronic excited state potential energy surfaces with simultaneous ultrafast X-ray scattering and spectroscopy. Chemical Science, 10(22), 5749–60.
Ji, M., Odelius, M., & Gaffney, K. J. (2010). Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution. SCIENCE, 328(5981), 1003–5.
Zhang, W., Kjaer, K. S., Alonso-Mori, R., Bergmann, U., Chollet, M., Fredin, L. A., … Gaffney, K. J. (2017). Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution. CHEMICAL SCIENCE, 8(1), 515–23.
Mara, M. W., Hadt, R. G., Reinhard, M. E., Kroll, T., Lim, H., Hartsock, R. W., … Solomon, E. I. (2017). Metalloprotein entatic control of ligand-metal bonds quantified by ultrafast x-ray spectroscopy. SCIENCE, 356(6344), 1276-+.
Wernet, P., Kunnus, K., JOSEFSSON, I., RAJKOVIC, I., Quevedo, W., Beye, M., … Foehlisch, A. (2015). Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)(5) in solution. NATURE, 520(7545), 78–81.
Kjaer, K. S., Kunnus, K., Harlang, T. C. B., Van Driel, T. B., Ledbetter, K., Hartsock, R. W., … Gaffney, K. J. (2018). Solvent control of charge transfer excited state relaxation pathways in [Fe(2,2 '-bipyridine)(CN)(4)](2-). PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20(6), 4238–49.