Department of Chemistry Seminar - Vibronic Couplings at Interfaces Revealed by Development of Interface-Specific 2D Electronic-Vibrational (i2D-EV) and 2D Vibrational-Electronic (i2D-VE) Spectroscopies

Speaker: Professor Yi RAO

Institution: Department of Chemistry and Biochemistry, Utah State University, USA

Hosted By: Professor Tengteng CHEN

Abstract

Vibronic coupling (VC) describes the interactions between electronic and vibrational motions and is crucial for understanding nonadiabatic processes, especially near conical intersections. VC plays a key role in fundamental photoinduced steps, including charge transfer, proton transfer, proton-coupled charge transfer, photoinduced isomerization, and energy transfer. These photoinduced relaxation processes at interfaces are central to fields such as solar energy conversion, photocatalysis, and photosynthesis.

While vibronic coupling at interfaces is expected to differ from bulk behavior due to the unique interfacial environment, it remains poorly understood. Here, we developed interface-specific two-dimensional electronic-vibrational sum frequency generation (i2D-EV) and interface-specific two-dimensional vibrational-electronic spectroscopy (i2D-VE) to probe these couplings. Using i2D-EV, we extracted the relative orientations and solvent correlations of electronic and vibrational transition dipoles at the interface. Complementing this, i2D-VE spectroscopy reveals the coupling between vibrational ground or excited states and the electronic states of molecules at surfaces and interfaces. These methodologies offer insights into the dynamic coupling of electronic and vibrational motions, extending the utility of the rich data obtained. Finally, we compare these techniques with traditional double-resonance sum frequency generation.