CCS Seminar Features Yoshitaka Tanimura, “Simulating, Modeling, and Analyzing Two-Dimensional THz-Raman Spectroscopies”

The Boston University Center for Computational Science will be hosting a seminar featuring Professor Yoshitaka Tanimura from the Department of Chemistry at Kyoto University, Japan.

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

12:00 PM on March 24, 2015

Physics Research Building, 3 Cummington Mall, Room 595

Abstract: 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. 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. 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.