Founded at Northwestern in June 2023, the Gaynor Group develops and uses new ultrafast multidimensional spectroscopies to understand how energy and charge move in molecules and materials, beginning from the earliest moments of photoexcitation through to relaxation in the environment. We are experimental physical chemists who combine high energy femtosecond lasers, nonlinear optics, and ultrahigh vacuum chambers to understand photochemical dynamics in ways not possible by other means. The pursuit of understanding how important photochemistry happens on the attosecond and femtosecond timescale is what drives us.
Charge Migration, Transfer, and Solvation in Molecules
We explore how pure electronic coherence and electron-electron correlation governs the earliest stages of molecular photochemical reactions, and how the onset of vibronic interactions from nuclear motions affect that coherence. Fundamentally, these dynamics are rooted in the boundaries of the Born-Oppenheimer Approximation. Some example dynamics of particular interest to us include coherent charge and energy transfer, passing through conical intersections, proton-coupled electron transfer, photoisomerization, and twisted intramolecular charge transfer. Potential applications of this knowledge can include eventually engineering coherence to favor particular photochemical outcomes.
Electronic and Excitonic Motion in Materials
Harnessing the motion of electrons and excitons is critical to developing new, more efficient optoelectronic, photovoltaic, and photocatalytic materials in thin film and solid phases. Characterizing the formation and coherent transport of excitons is a central goal for next generation materials. We use multidimensional spectroscopies that locally probe photoexcited carriers with elemental, oxidation state, spin state, and vibrational specificity on attosecond to femtosecond timescales. Some examples where these dynamics are of interest include layered Van der Waals materials, quantum materials, and quantum dot-ligand complexes.
Instrumentation and Method Development
We operate on, and advance, the frontiers of nonlinear spectroscopy in order to understand photochemical events from new perspectives; this helps us build a more global picture of how photochemistry happens. Our tool of choice is multidimensional spectroscopy as it uniquely reveals dynamic correlations between excited and detected degrees of freedom and directly resolves coherent dynamics. We devise new experimental methods using a combination of tabletop attosecond extreme ultraviolet (20-100 eV) pulses, broadband few-cycle pulses covering 250 nm – 2400 nm, and mid-IR pulses covering 2500 nm – 15000 nm and longer. We also develop the theory to interpret our experiments both within our group and in collaboration with professional theoreticians.
We gratefully acknowledge the following organizations for their support of our research:
