Electronic coherence formation in the Radiationless S₂ decay of pyrazine: Quantum Ehrenfest simulations focused on the branching space of the conical intersection
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Published version
Author(s)
Moore, Luke J
Bearpark, Michael J
Worth, Graham A
Robb, Michael A
Type
Journal Article
Abstract
We investigate the formation of electronic coherences in pyrazine following excitation to the S2 1B2u (ππ*) state (D2h) and relaxation via a conical intersection (CI) to the S1 1B3u (nπ*) state. In our Quantum Ehrenfest (Qu-Eh) simulations, Gaussian wavepackets (GWPs) are started in the positive and negative directions of all the selected normal modes. The GWPs moving along the derivative coupling vector cross the CI and generate coherences from time zero. The effect nevertheless cancels in the total wavefunction because the wavepackets have opposite geometric phases. Thus, our results support the theoretical conjecture which states that coherences should not be observable if the intersecting states have different Abelian point group symmetries at the Franck-Condon (FC) point. However, if initial conditions start with a small admixture of the second coupled state, in this case the S1 1B3u (nπ*) state, rather than a pure S2 state, one generates an initial gradient along either the positive or negative direction of the derivative coupling vector, thus biasing the motion of the wavepacket so that the coherence becomes non-zero.
Date Issued
2026-06-01
Date Acceptance
2026-01-31
Citation
Chemical Physics, 2026, 605
ISSN
0301-0104
Publisher
Elsevier
Journal / Book Title
Chemical Physics
Volume
605
Copyright Statement
© 2026 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Publication Status
Published
Article Number
113115
Date Publish Online
2026-02-02