Quantum Dynamics of Isomerization Processes

Isomerization—the rearrangement of atoms within a molecule to form distinct structural forms—lies at the heart of many chemical and biological transformations. When barrier heights approach or exceed thermal energies, classical transition‐state theory becomes inadequate and quantum effects such as tunnelling, coherence and zero‐point motion dominate. In condensed and interfacial environments, isomerization may proceed via transitions between discrete bound states rather than over a continuous barrier, with energy exchange mediated by phonons or solvent fluctuations. Such processes underpin photochemical switches, enzymatic catalysis and surface‐bound reactions, and feed into broader applications from solar energy conversion to astrochemical synthesis. Recent advances combine high‐resolution spectroscopy, multireference quantum chemistry, machine‐learning potentials and novel rate theories to reveal that isomerization rates may defy simple mass‐dependent trends, that specific reactant–product state pairs (‘gateways’) can govern the overall kinetics, and that environmental couplings profoundly reshape both barrier heights and tunnelling probabilities. These insights highlight the need to treat isomerization as a genuinely quantum‐mechanical, system‐specific phenomenon, rather than as a purely classical activated process.

Research from Nature Portfolio

Recent studies have illuminated the role of discrete tunnelling gateways in condensed‐phase isomerization. Experimental measurements of isotopologue‐specific rates for carbon monoxide inversion on alkali halide surfaces reveal a non‐monotonic dependence of tunnelling probability on atomic mass. A new quantum rate theory describes transitions between sub‐barrier bound states interacting with a phonon bath, showing that only certain state pairs act as efficient ‘gateways’ through the barrier. This model explains why heavier isotopologues may tunnel faster than lighter ones and predicts that heavy‐atom tunnelling can significantly contribute to ground‐state isomerization—a departure from textbook expectations.

Quantum Dynamics of Isomerization Processes publication trend

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

Technical terms

Isomerization: Rearrangement of a molecule’s atoms to form a distinct structural isomer without changing its molecular formula.

Quantum tunnelling: The passage of a particle through an energy barrier higher than its classical kinetic energy, enabled by its wave‐like nature.

Potential energy surface (PES): A multidimensional surface representing the energy of a system as a function of nuclear coordinates, used to describe reaction pathways.

Isotopologue: A variant of a molecule in which one or more atoms are replaced by their isotopes, altering mass without changing electronic structure.

Quantum gateway: A specific pair of reactant and product bound states whose coupling through environmental modes dominates the tunnelling rate in an isomerization reaction.

References

1. Condensed-phase isomerization through tunnelling gateways. Nature (2022).
2. CO Inversion on a NaCl(100) Surface: A Multireference Quantum Embedding Study. The Journal of Physical Chemistry A (2023).
3. Multidimensional Neural Network Interatomic Potentials for CO on NaCl(100). The Journal of Physical Chemistry C (2024).
4. Manipulating tunnelling gateways in condensed phase isomerization. Natural Sciences (2023).