Surface crossing and energy flow in many-dimensional quantum systems

Area of Science:

• Physical Chemistry
• Quantum Dynamics
• Molecular Spectroscopy

Background:

• Energy flow in molecules is crucial for processes like photosynthesis.
• This flow typically involves quantum transport through a dense network of resonant states.
• Anharmonic vibrational Fermi resonances and electronic surface crossings drive chaotic motion and energy redistribution.

Purpose of the Study:

• To investigate the interplay between vibrational energy flow and nonadiabatic electronic state mixing.
• To develop a theoretical framework predicting the transition between localized and global quantum dynamics.
• To test theoretical predictions using a model relevant to photosynthetic energy transfer.

Main Methods:

• Generalized Logan-Wolynes theory for quantum energy flow in two-electronic-state systems.
• Development of a phase diagram delineating localized dynamics from global energy flow.
• Explicit numerical solution of the time-dependent Schrödinger equation for a ten-dimensional model.

Main Results:

• Demonstrated that nonadiabatic coupling enhances vibrational energy flow, while vibrational couplings promote electronic state mixing.
• The generalized theory successfully predicts a phase boundary for quantum energy flow.
• Numerical simulations of a photosynthetic reaction center model showed good agreement with theoretical predictions.

Conclusions:

• Interconnected electronic and vibrational couplings govern molecular energy dynamics.
• The developed phase diagram offers a valuable tool for understanding quantum transport in complex molecular systems.
• Theoretical insights are crucial for controlling energy flow in molecular processes.