Fifth-order raman spectrum of an atomic liquid: simulation and instantaneous-normal-mode calculation

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Obtaining the 5th-order Raman spectrum of liquids is challenging due to experimental artifacts and computational difficulties.
• Previous theoretical models struggled to accurately capture the complex dynamics of liquids at this spectral order.

Purpose of the Study:

• To report the first microscopic numerical simulation of the 5th-order Raman signal in a liquid.
• To investigate the role of dynamical anharmonicity in liquid dynamics using advanced spectroscopic methods.

Main Methods:

• Development of a novel microscopic numerical simulation approach.
• Calculation of the 5th-order Raman spectrum for a liquid system.
• Comparison with the instantaneous-normal-mode (INM) treatment, a microscopic model based on coherent harmonic modes.

Main Results:

• Successfully performed the first microscopic numerical simulation of a liquid's 5th-order Raman spectrum.
• The simulation results highlight significant contributions from dynamical anharmonicity.
• Comparison with the INM treatment demonstrates the limitations of harmonic mode approximations in capturing anharmonic effects.

Conclusions:

• The developed simulation provides a new theoretical tool for studying complex liquid dynamics.
• Dynamical anharmonicity plays a crucial role in shaping the 5th-order Raman spectrum of liquids.
• This work advances the understanding of molecular interactions and dynamics in condensed phases.