In this seminar, I will discuss two developments of ultrafast nonlinear IR spectroscopy for exotic molecular materials: (1) 2D IR spectroscopy for molecular vibrational polaritons and (2) heterogeneous water dynamics templated by self-assembled materials. Both show the advantages of ultrafast nonlinear IR spectroscopic technique to decipher hidden physics of exotic molecular materials.
2D IR of Molecular Polaritons. Molecular vibrational polaritons, hybrid half-light, half-matter quasiparticles, are studied using ultrafast coherent 2D IR spectroscopy. Molecular vibrational-polaritons are anticipated to open opportunities for new photonic and molecular phenomena. Many of these developments hinge on fundamental understanding of physical properties of molecular vibrational polaritons. Using 2D IR spectroscopy to study vibrational-polaritons, we obtained results that challenge and advance both polariton and spectroscopy fields, which invokes new development of theory for the spectroscopy, observation of new nonlinear optical effects and unexpected responses from hidden dark states These results will have significant implications in novel infrared photonic devices, lasing, molecular quantum simulation, as well as new chemistry by tailoring potential energy landscapes.
Heterogeneous water dynamics templated by self-assembled materials. We report observations of mesoscopically homogeneous but macroscopically heterogenous water dynamics in self-assembled materials by a new, spatially resolved infrared (IR) pump vibrational sum frequency generation (VSFG) probe microscope. We found that the strong hydrogen-bond interactions between host molecules and nearby water not only template nearby water networks to adopt the chirality of self-assembled materials, but also induce resonant energy transfer from ?-CD to nearby water, which is heterogeneous among domains, but uniform within domains.






Wei Xiong (UC-San Diego)