Electron-Nuclear Dynamics in Nonadiabatic Processes

Electron–nuclear dynamics in nonadiabatic processes explores the interplay between electronic motion and nuclear movement when the Born–Oppenheimer approximation breaks down. In many photochemical and photophysical events, electronic wavepackets traverse regions where potential energy surfaces intersect or approach closely, triggering rapid transfers of energy and charge. This coupling gives rise to phenomena such as conical intersections, wavepacket bifurcation, ultrafast electronic coherence and energy redistribution, all of which shape the outcome of chemical reactions and energy-conversion processes. Theoretical and computational approaches—including mixed quantum–classical frameworks, semiclassical propagation, surface hopping and exact factorization—have been developed to capture these intricate dynamics. Insights from this field inform the design of light-harvesting materials, molecular switches and catalysts, and underpin advances in attosecond spectroscopy that resolve electron and nuclear motion in real time.

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Recent studies have brought new clarity to how electronic and nuclear fluxes emerge and evolve under nonadiabatic coupling. One line of work introduces the concept of quantum chaos in molecular systems, showing that wavepacket bifurcation and merging in nonadiabatic regimes lead to irregular fluxes of electrons and energy. This framework, termed intra-molecular nonadiabatic electronic energy redistribution, extends classical notions of chaos to fully quantum electron–nuclear dynamics and highlights its impact on unimolecular decomposition and energy redistribution pathways.

Another contribution focuses on the conservation of electronic probability current in low-energy reactions. It demonstrates that even weak nonadiabatic effects—insufficient to alter nuclear trajectories significantly—play a critical role in reproducing adiabatic evolutions of electronic density. By analysing the divergence of nonadiabatic flux and its relation to time-dependent density changes, this work clarifies how common truncation schemes can violate flux conservation and proposes strategies to achieve consistent current calculations.

A complementary investigation disentangles electronic and nuclear contributions to flux under both nonadiabatic and multiple-configuration adiabatic dynamics represented in the Born–Huang expansion. It reveals that interference among adiabatic wavepacket components can generate fluxes similar to those induced by explicit nonadiabatic couplings. The systematic classification of these fluxes deepens understanding of quantum interference effects and offers a rigorous way to distinguish genuine nonadiabatic transitions from adiabatic coherence phenomena.

Electron-Nuclear Dynamics in Nonadiabatic Processes publication trend

The graph below shows the total number of articles in electron-nuclear dynamics in nonadiabatic processes across all publications each year (not limited to Nature Index journals).

Technical terms

Born–Oppenheimer approximation: A separation of electronic and nuclear motions under the assumption that nuclei move much more slowly than electrons.

Nonadiabatic process: A phenomenon in which electronic and nuclear degrees of freedom become strongly coupled, invalidating the Born–Oppenheimer separation.

Potential energy surface: A multidimensional landscape describing how the electronic energy of a molecule varies with nuclear coordinates.

Conical intersection: A point or seam where two potential energy surfaces of different electronic states become degenerate, allowing rapid state transitions.

Wavepacket: A superposition of quantum states localised in position or momentum space, used to model time-dependent evolution.

Electronic flux: The quantum probability current associated with electronic motion, quantifying how electron density flows over time.

References

1. Quantum Chaos in the Dynamics of Molecules. Entropy (2022).
2. On the molecular electronic flux: Role of nonadiabaticity and violation of conservation. The Journal of Chemical Physics (2021).
3. Electronic and nuclear fluxes induced by quantum interference in the adiabatic and nonadiabatic dynamics in the Born-Huang representation. The Journal of Chemical Physics (2019).