Transient Symmetry Controls Photo Dynamics near Conical Intersections

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Excited-state chemistry currently lacks generalized symmetry rules, hindering chemical intuition.
• Femtochemistry studies often focus on individual cases, making it difficult to establish broad principles.
• Understanding excited-state dynamics is crucial for controlling chemical reactions.

Purpose of the Study:

• To investigate the role of molecular symmetry in ultrafast internal conversion (IC).
• To map vibrational coherence during excited-state transitions in cyclic tertiary amines.
• To explore the potential for developing symmetry-based selection rules for excited-state processes.

Main Methods:

• Analysis of vibrational coherence in the initial wavepacket.
• Dependence of internal conversion on molecular symmetry in cyclic tertiary amines.
• Ultrafast spectroscopy techniques to probe excited-state dynamics.

Main Results:

• Molecular symmetry significantly influences the preservation of vibrational coherence during electronic state transitions.
• Even a transiently accessible more symmetric structure is sufficient to preserve vibrational coherence.
• Specific cyclic tertiary amines exhibit symmetry-dependent coherence preservation during ultrafast internal conversion.

Conclusions:

• Molecular symmetry is a key factor in controlling excited-state dynamics and internal conversion pathways.
• The possibility of a more symmetric structure, even if transient, facilitates coherence preservation.
• These findings contribute to establishing generalized symmetry rules for excited-state chemistry.