Full molecular dynamics simulations of liquid water and carbon tetrachloride for two-dimensional Raman spectroscopy in the frequency domain

TL;DR

This paper uses molecular dynamics simulations to calculate frequency-domain 2D Raman signals for water and carbon tetrachloride, revealing mechanisms like mode coupling and polarizability nonlinearities that help interpret advanced spectroscopic measurements.

Contribution

It introduces a hybrid MD simulation approach to predict 2D Raman signals, elucidating underlying molecular mechanisms and aiding analysis of single-beam 2D spectra.

Findings

Identified anharmonic mode-mode coupling effects.

Demonstrated nonlinear polarizability contributions.

Predicted signal profiles matching experimental observations.

Abstract

Frequency-domain two-dimensional Raman signals, which are equivalent to coherent two-dimensional Raman scattering (COTRAS) signals, for liquid water and carbon tetrachloride were calculated using an equilibrium-nonequilibrium hybrid MD simulation algorithm. We elucidate mechanisms governing the 2D signal profiles involving anharmonic mode-mode coupling and the nonlinearities of the polarizability for the intermolecular and intramolecular vibrational modes. The predicted signal profiles and intensities can be utilized to analyze recently developed single-beam 2D spectra, whose signals are generated from a coherently controlled pulse, allowing the single-beam measurement to be carried out more efficiently.