Singlet Fission Dynamics Controlled by an Electronic Crossing Seam

Area of Science:

• Photochemistry
• Theoretical Chemistry
• Quantum Dynamics

Background:

• Electronic degeneracies (conical intersections, avoided crossings) are crucial for photochemical processes.
• The role of these degeneracies in excited-state chemical reactivity remains incompletely understood.

Purpose of the Study:

• To investigate the control mechanism of singlet fission dynamics in the H4 molecule.
• To elucidate the role of the S1/S2 crossing seam in singlet fission.

Main Methods:

• Theoretical study of singlet fission dynamics.
• Analysis of the S1/S2 crossing seam.
• Quantum geometric perspective for understanding reactivity.

Main Results:

• Singlet fission dynamics in H4 are governed by the S1/S2 crossing seam.
• The nuclear wavepacket follows and turns around at the seam.
• An extended crossing seam can effectively block the reaction channel.

Conclusions:

• A quantum geometric perspective provides an intuitive understanding of the observed effects.
• A novel mechanism for controlling photochemical reactions via crossing seam geometry is identified.
• The findings contribute to understanding the mechanism of singlet fission.