Two-dimensional electronic spectra from trajectory-based dynamics: Pure-state Ehrenfest, spin-mapping, and mean...

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Spectroscopy

Background:

• Two-dimensional electronic spectroscopy (2DES) reveals complex electron dynamics.
• Simulations are crucial for interpreting 2DES data.
• Existing methods have limitations in accuracy and computational cost.

Purpose of the Study:

• To develop and compare trajectory-based nonadiabatic dynamics methods for simulating 2DES spectra.
• To improve the accuracy of simulations for electronically nonadiabatic processes.
• To assess the performance of different methods against exact spectra.

Main Methods:

• Developed an improved pure-state Ehrenfest approach using equatorial pure state decomposition.
• Implemented spin mapping during pump-probe delay for enhanced accuracy.
• Compared Ehrenfest, spin mapping, and mean classical path approximations.
• Validated methods against exact spectra of Frenkel exciton models (dimer and FMO complex).

Main Results:

• The improved Ehrenfest method provides a more accurate simulation of 2DES.
• Spin mapping during pump-probe delay enhances accuracy but increases computational cost.
• Mean classical path approximation offers a simpler, less computationally intensive alternative.
• All tested methods show varying degrees of accuracy in reproducing linear, pump-probe, and 2DES spectra.

Conclusions:

• Trajectory-based dynamics methods offer valuable insights into nonadiabatic dynamics.
• The choice of method involves a trade-off between accuracy and computational expense.
• These simulations aid in the interpretation of complex 2DES experiments.