Fluorescence in quantum dynamics: Accurate spectra require post-mean-field approaches.

Area of Science:

• Quantum dynamics
• Spectroscopy
• Theoretical chemistry

Background:

• Modeling real-time fluorescence with vibronic resolution is complex, requiring coupled quantum mechanics for light-matter interactions and phonons.
• Decoupling internal conversion and radiative relaxation based on timescale differences simplifies modeling.

Purpose of the Study:

• To simulate electron dynamics in fluorescence using a Redfield-derived master equation.
• To evaluate the accuracy of the coherent electron electric-field dynamics (CEED) semiclassical model for the radiative stage of fluorescence.
• To compare CEED results with full quantum electrodynamics (QED) for light-matter interaction modeling.

Main Methods:

• Simulated electron dynamics using a master equation from the Redfield formalism.
• Employed the coherent electron electric-field dynamics (CEED) semiclassical model for radiative relaxation.
• Compared CEED predictions against full quantum electrodynamics (QED) calculations.

Main Results:

• The CEED model accurately predicts emission frequencies, aligning with QED results.
• CEED fails to reproduce correct spectral amplitudes during de-excitation to closely lying states.
• This amplitude inaccuracy is attributed to the inherent mean-field nature of CEED.

Conclusions:

• The CEED model offers accurate prediction of emission peak positions without prior Hamiltonian knowledge.
• CEED's mean-field approximation limits its accuracy for spectral amplitudes in specific de-excitation scenarios.
• This study highlights a critical limitation of CEED for light-matter interaction studies involving complex electronic states.