Ultrafast Electronic Relaxation through a Conical Intersection: Nonadiabatic Dynamics Disentangled through an...

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Dynamics

Background:

• 4-(N,N-dimethylamino)benzonitrile (DMABN) is a dual fluorescent molecule exhibiting nonadiabatic transitions.
• Understanding its short-time dynamics is crucial for photochemistry and spectroscopy.

Purpose of the Study:

• To model the short-time dynamics of gas-phase and partially solvated DMABN.
• To compare theoretical calculations with time-resolved fluorescence measurements.
• To investigate nonadiabatic transitions through a conical intersection.

Main Methods:

• Employing surface hopping trajectories for mixed quantum-classical dynamics.
• Calculating the mixed quantum-classical density matrix and ensemble-averaged transition dipole moment.
• Introducing a diabatization scheme based on oscillator strength to convert TDDFT adiabatic states to L_a and L_b diabatic states.

Main Results:

• The rate of relaxation via emission to the ground state is approximately 50% slower than adiabatic population relaxation.
• Calculated adiabatic rates are consistent with previous theoretical findings.
• No significant decoherence effects were observed.

Conclusions:

• The developed diabatization procedure provides an explicit picture of dynamics in the branching plane.
• The findings raise questions regarding geometric phase effects in complex molecular systems.
• The study highlights the importance of accurate modeling for understanding photochemical processes.