Dr. Renee Frontiera, Northwestern University

Obtaining structural snapshots of reacting molecules in real time with ultrafast vibrational and surface-enhanced spectroscopies

This talk will focus on probing chemical reactivity through the use of an innovative technique called Femtosecond Stimulated Raman Spectroscopy (FSRS), which is capable of following vibrational structure with simultaneous high spectral and temporal resolution.  By acquiring complete structural snapshots of evolving molecules on the femtosecond time scale, one can map out portions of a reactive multidimensional potential energy surface, leading to a complete mechanistic understanding of chemical reaction dynamics. I will focus on two applications of the FSRS technique, first on the vibrationally-driven excited state proton transfer reaction in the Green Fluorescent Protein (see figure), and second on the interfacial electron transfer process in dye-sensitized TiO2 nanoparticles. I will then discuss recent efforts to extend FSRS to the single molecule regime by the use of the enhanced electromagnetic fields present near plasmonic nanostructures.This work resulted in the invention of Surface Enhanced-Femtosecond Stimulated Raman spectroscopy, a novel stimulated surface enhanced Raman technique which probes the ultrafast response of molecules near excited plasmons.