Quantum Dynamics of Chemical and Molecular Reactions

Quantum dynamics lies at the heart of our understanding of how molecules interact, transform and respond to external stimuli. Unlike classical descriptions that treat nuclei and electrons as point particles following definite trajectories, quantum dynamics accounts for wave–particle duality, coherence and tunnelling through energy barriers that would be insurmountable in a purely classical picture. These phenomena govern processes as diverse as hydrogen transfer in enzymes, energy flow in atmospheric chemistry and the formation of complex molecules in interstellar space. Advances in ultrafast spectroscopy, crossed-beam experiments and high-performance computing have enabled the real-time observation and simulation of wavepacket evolution on potential energy surfaces, revealing the interplay of electronic and nuclear motions. Conical intersections and geometric phase effects are now recognised as critical junctions where electronic states exchange character, shaping reaction selectivity and yield. Theoretical frameworks such as time-dependent wavepacket propagation, semiclassical instanton theory and machine-learning-enhanced potential surfaces have extended quantitative predictions to ever-more complex systems. Collectively, these tools are unlocking new opportunities for controlling reactivity at the quantum level, with implications for catalyst design, quantum materials and our fundamental picture of chemical change.

Research from Nature Portfolio

Recent studies have directly visualised quantum interference patterns arising from conical intersection dynamics in prototype exchange reactions. State-of-the-art crossed-molecular-beam experiments combined with quantum reactive scattering have unveiled backward oscillations in angular distributions at sub-electron-volt collision energies, providing the first clear evidence of a geometric phase effect below a conical intersection. These measurements demonstrate how subtle phase shifts in partial-wave contributions modulate reaction probabilities and open avenues for phase-sensitive control of product channels. Parallel theoretical analyses have employed time-dependent wavepacket calculations on high-accuracy diabatic potential energy surfaces to dissect the role of van der Waals saddles versus wells in complex-forming reactions, revealing that long-range interactions can invert steric preferences and give rise to unexpected resonance structures in cross-section data.

Quantum Dynamics of Chemical and Molecular Reactions publication trend

The graph below shows the total number of articles in quantum dynamics of chemical and molecular reactions across all publications each year (not limited to Nature Index journals).

Technical terms

Conical intersection: A point of degeneracy between two electronic states where potential energy surfaces intersect, enabling rapid nonadiabatic transitions.

Geometric phase effect: A quantum phase shift acquired by a wavefunction when it encircles a conical intersection, affecting interference patterns.

Tunnelling: The quantum phenomenon whereby particles traverse energy barriers higher than their classical kinetic energy.

Instanton theory: A semiclassical method that approximates tunnelling rates by identifying dominant periodic paths (“instantons”) on a discretised path-integral surface.

Potential energy surface (PES): A multidimensional landscape that represents the energy of a molecular system as a function of nuclear coordinates, guiding quantum and classical dynamics.

References

1. Observation of geometric phase effect through backward angular oscillations in the H + HD → H2 + D reaction. Nature Communications (2024).
2. Dynamical importance of van der Waals saddle and excited potential surface in C(1D)+D2 complex-forming reaction. Nature Communications (2017).
3. Hydrogen‐Atom Tunneling in a Homochiral Environment. Angewandte Chemie International Edition (2023).
4. Ring-Polymer Instanton Tunneling Splittings of Tropolone and Isotopomers using a Δ‑Machine Learned CCSD(T) Potential: Theory and Experiment Shake Hands. Journal of the American Chemical Society (2023).