Colloquium: Cavity-Enabled Enhancement of Ultrafast Intramolecular Vibrational Redistribution over Pseudorotation

ABSTRACT

Vibrational Strong Coupling (VSC) between molecular vibrational modes and microcavity photon modes yields a few polaritons (light-matter modes) and many dark modes (with negligible photonic character). Although VSC is reported to alter thermally-activated chemical reactions, its mechanisms remain opaque. To shed light on this problem, we followed ultrafast dynamics of a simple unimolecular vibrational energy exchange in Fe(CO)5 under VSC, which showed two competing channels: pseudorotation and intramolecular vibrational-energy redistribution (IVR), by using two-dimensional infrared (2D IR) spectroscopy. We found that, under polariton excitation, energy exchange was overall accelerated, with IVR becoming faster and pseudorotation being slowed down. However, dark mode excitation revealed unchanged dynamics compared to outside of cavity, with pseudorotation dominating. Thus, despite controversies of thermally-activated VSC modified chemistry, our work showed VSC can indeed alter chemistry upon non-equilibrium preparation of polaritons.

BIOGRAPHY

Prof. Tengteng Chen obtained his BSc in Applied Physics in 2013 from the Special Class for Gifted Young (SCGY) at University of Science and Technology of China (USTC), and completed his Ph.D. in Chemistry at Brown University in 2020 (Advisor: Prof. Lai-Sheng Wang). Subsequently, he joined Prof. Wei Xiong's group at UC San Diego as a postdoctoral scholar. In 2023, Prof. Chen joined the Department of Chemistry at HKUST as an assistant professor. His current research centers on exploring the mechanisms and dynamics of molecular systems and chemical reactions under strong light-matter interactions using ultrafast spectroscopy. Prof. Chen has published more than 20 articles as the first (co-first) author in esteemed journals, including Science, Annu. Rev. Phys. Chem., PNAS, Nat. Commun., and Angew. Chem. Int. Ed.. Among his accolades is the Young Elite Scientists Sponsorship Program by Chinese Association of Science and Technology (first from Hong Kong).