Dynamics of benzene excimer formation from the parallel-displaced dimer

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Excimers are crucial in excited-state processes like fluorescence quenching and singlet-fission.
• Understanding excimer dynamics is key to controlling photochemical reactions.

Purpose of the Study:

• To investigate the ultrafast dynamics of benzene excimer formation.
• To elucidate the correlation between nuclear and electronic structure during excimer formation.

Main Methods:

• Simulated nonadiabatic surface-hopping dynamics.
• Employed the second-order algebraic diagrammatic construction (ADC(2)) method.
• Analyzed benzene dimer behavior within the first 2 picoseconds post-excitation.

Main Results:

• Benzene rings approach a parallel-stacked excimer geometry in 0.5-1.0 ps.
• Excimers persist for 0.1-0.4 ps before dissociation due to vibrational energy.
• Significant widening of the S1-S2 energy gap observed in the excimer region.
• Decreased ring distance correlates with enhanced charge transfer.
• Fast exciton transfer leads to equal exciton probability in each ring by ~1.0 ps.

Conclusions:

• Provides detailed insight into benzene excimer formation mechanisms.
• Highlights the interplay between nuclear motion and electronic structure.
• Confirms rapid exciton delocalization in benzene dimers.