Nonadiabatic Photochemistry Induced by Inaccessible Conical Intersections

Area of Science:

• Photochemistry
• Quantum Dynamics
• Chemical Physics

Background:

• Conical intersections are crucial in photochemistry, mediating ultrafast nonradiative decay from excited states.
• Key diagnostics include ultrafast electronic dynamics, minimal fluorescence, and coherent wavepacket transfer.
• These attributes are traditionally linked to pathways directly through the conical intersection.

Purpose of the Study:

• To investigate nonadiabatic transfer dynamics in photochemical processes.
• To determine if conical intersections are essential for observed ultrafast decay phenomena.
• To reassess the diagnostic features and conceptual framework of conical intersections in photochemistry.

Main Methods:

• Generalized quantum dynamics simulations were employed.
• Simulations analyzed the behavior of excited vibrational wavepackets.
• Investigated wavepacket transfer efficiencies and pathways relative to conical intersections.

Main Results:

• Coherent nonadiabatic transfer of vibrational wavepackets can occur without reaching the conical intersection.
• Wavepackets can remain distant from the conical intersection during transfer.
• Substantial nonadiabatic transfer and ultrafast efficiencies were observed even when avoiding the conical intersection.

Conclusions:

• The diagnostic features of conical intersections are not exclusive to pathways passing through them.
• Alternative pathways, not involving direct intersection traversal, can mimic conical intersection signatures.
• The paradigm of conical intersection pathways in photochemistry may require reevaluation.