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CCS Seminar
Tuesday - March 24, 2015
12:00 Noon
Physics Research Building - Room 595
3 Cummington Mall

Professor Yoshitaka Tanimura
Department of Chemistry, Kyoto University, Kyoto 606-8502, Japan

"Simulating, Modeling, and Analyzing Two-Dimensional THz-Raman Spectroscopies "

Understanding dynamics in complex environments of molecular liquids and biological systems has been a central topic of investigation in chemistry and biology, because many important chemical processes occur exclusively in such media. Recently, two-dimensional (2D) THz-Raman spectroscopy has been used to investigate the intermolecular modes of liquid.[1] We calculate such 2D spectroscopy signals for liquid water, methanol, and formamide using an equilibrium-non-equilibrium hybrid MD simulation algorithm originally developed for 2D Raman spectroscopy.[2] These signals are analyzed in terms of anharmonicity and nonlinear polarizability of vibrational modes using a Brownian oscillator (BO) model with linear-linear (LL) and square-linear (SL) system-bath interactions from the hierarchal equations of motion approach for a non-Markovian noise. All of the characteristic 2D profiles of the signals obtained from MD are reproduced using the LL+SL BO model indicating that this model captures the essential features of the inter-molecular motion. We analyze the fitted 2D profiles in terms of anharmonicity, nonlinear polarizability, and dephasing time. The origin of the echo peaks of librational motion and the elongated peaks parallel in the probe direction are elucidated by the optical Liouville paths.[3] References [1] J. Savolainen, S. Ahmed, and P. Hamm, Proc. Natl. Acad. Sci. U.S.A. 110, 20402 (2013). [2] H. Ito, T. Hasegawa, and Y. Tanimura, J. Chem. Phys. 141, 124503 (2014). [3] T. Ikeda, H. Ito, and Y. Tanimura, submitted. comes from the Department of Energy, Samsung Electric Corporation, and Boston University.





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