Full molecular dynamics simulations of molecular liquids for single-beam spectrally controlled two-dimensional Raman spectroscopy

Abstract

Single-beam spectrally controlled (SBSC) two-dimensional (2D) Raman spectroscopy is a unique 2D vibrational measurement technique utilizing trains of short pulses that are generated from a single broadband pulse by pulse shaping. This approach overcomes the difficulty of 2D Raman spectroscopy in dealing with small-signal extraction and avoids complicated low-order cascading effects, thus providing a new possibility for measuring the intramolecular and intermolecular modes of molecular liquids using fifth-order 2D Raman spectroscopy. Recently, for quantitatively investigating the mode–mode coupling mechanism, Hurwitz et al. [Opt. Express 28, 3803 (2020)] have developed a new pulse design for this measurement to separate the contributions of the fifth- and third-order polarizations, which are often overlapped in the original single-beam measurements. Here, we describe a method for simulating these original measurements and the new 2D Raman measurements on the basis of a second-order response function approach. We carry out full molecular dynamics simulations for carbon tetrachloride and liquid water using an equilibrium–nonequilibrium hybrid algorithm, with the aim of explaining the key features of the SBSC 2D Raman spectroscopic method from a theoretical point of view. The predicted signal profiles and intensities provide valuable information that can be applied to 2D spectroscopy experiments, allowing them to be carried out more efficiently.

Autobiography of Yoshitaka Tanimura

“…To facilitate our research, Taisuke developed a water potential for the spectral analysis of intermolecular and intramolecular vibrations (88). Nobuhiro Ito and Ju-Yeon Jo then simulated and analyzed 2D THz-Raman (104,116), 2D IR-Raman (113), and single-beam 2D Raman spectra (134). Through the MD investigations, we collaborated with experimentalists, including Dwayne (79) and Peter Hamm, although Peter now may be better described as a theorist.…”

Accelerating Molecular Vibrational Spectra Simulations with a Physically Informed Deep Learning Model

“…Infrared (IR) and Raman spectroscopies , and their multidimensional extensions are high-precision techniques widely used for the characterization of molecular vibrations and vibrational energy transfer/redistribution. Hence, accurate theoretical simulation of IR and Raman spectra has always been on the “to-do list” of computational chemistry. − The traditional approach to the calculation of IR/Raman spectra of not-too-large molecules in the gas phase is based on the construction of (ab initio parametrized) molecular Hamiltonians . This methodology, in combination with appropriate numerical methods, can take into account finite temperature effects, anharmonicities, intermode couplings, internal energy redistribution, and so forth.…”