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Center for Nonlinear Studies |
Terahertz (THz) spectroscopy can be utilized to study many important physical and chemical phenomena in solid-state materials, such as lattice dynamics, phase transitions, transient conductivity and charge-carrier mobility. Presented will be the investigations of the structure and vibrational dynamics of molecular crystals by time-domain THz spectroscopy, and the computational treatments of the systems by solid-state density functional theory (DFT). Low-frequency lattice vibrations of molecular crystals are primarily governed by the particular set of non-covalent intermolecular interactions present in the system. Accurately modeling the complex potential energy surfaces of molecular systems requires augmentation of common DFT methods with corrections to account for weak London-type dispersion interactions. Additionally, modifications to the dispersion parameters can be tailored to further improve the results of the structural and frequency calculations. Understanding the relationship between crystalline structure, non-covalent interactions, and lattice vibrational dynamics is important for the interpretation of THz spectra in identifying crystalline forms, and also for guiding the prediction and design of new materials withdesired properties. Building from these fundamental studies of examining the interactions between THz radiation and matter, recent advances in the generation of high-energy THz pulses have opened up the emerging fields of nonlinear-THz and THz pump-probe spectroscopies. Using high-amplitude THz fields in conjunction with arbitrary manipulations of phase and polarization through optical pulse shaping techniques has the potential for controlling the coherent interactions of light and matter. Some desirable outcomes are the capabilities for directed chemical reactions, crystalline phase transitions, high-rate optical switching and charge transfer, and aid in the design of advanced functional materials.
Host: Jason Scharff