2D spectroscopies from condensed phase dynamics: Accessing third-order response properties from equilibrium...

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Third-order response is crucial for interpreting nonlinear spectroscopies (2D-IR, 2D-ES, 2D-SFG).
• These techniques offer detailed insights into electronic and vibrational states, couplings, and energy exchange in condensed phases.
• Existing computational methods struggle to reconcile exact quantum expressions with practical atomistic dynamics simulations for large systems.

Purpose of the Study:

• To develop a new formulation of the third-order response compatible with practical computational dynamics methods.
• To enable accurate simulation and interpretation of multidimensional nonlinear spectroscopies for condensed phase systems.
• To provide a physically transparent framework for understanding complex spectroscopic features.

Main Methods:

• Formulating the third-order response using equilibrium symmetrized Kubo transformed correlation functions.
• Employing classical dynamics and Ring Polymer Molecular Dynamics (RPMD) for simulations.
• Calculating the third-order response for model systems.

Main Results:

• The developed formulation successfully captures anharmonic features like vertical splittings and peak shifts.
• Demonstrated the utility and accuracy of the approach using classical dynamics and RPMD.
• Provided a physically transparent framework for analyzing multidimensional spectroscopies.

Conclusions:

• The new formulation bridges the gap between theoretical third-order response and practical computational methods.
• This approach enhances the simulation and interpretation of complex nonlinear spectroscopic data.
• Offers a valuable tool for studying molecular dynamics and energy transfer in condensed phase systems.