Exploring Vibrational Polariton Dynamics with Ultrafast Two-Dimensional Infrared Spectroscopy

Vibrational strong coupling (VSC) offers a new approach to manipulate reaction thermodynamics, vibrational energy flow, and intermolecular interactions. The complex energy relaxation, transfer, and dephasing processes in vibrational polaritons are ideally suited for study by ultrafast infrared spectroscopy, particularly two-dimensional infrared (2D-IR), which has become a major tool to unravel vibrational dynamics in general. This talk will introduce and review the key principles and molecular observables central to 2D-IR, while demonstrating its application to a vibrational polariton system. For our first implementations of VSC we have chosen a tripodal transition metal carbonyl complex, methyl cycopentadienyl manganese tricarbonyl (MeCMT), which has two strong CO stretching bands near 2000 cm-1 separated by roughly 80 cm-1. Using a cavity with a free spectral range that closely matches this energy splitting, we establish strong coupling between the molecule and two adjacent cavity modes. The 2D-IR spectra show significant coupling between the two branches of polaritons, as well as extensive coherences and signatures for coherence transfer.