Interatomic Coulombic Decay in Molecular Systems

Interatomic Coulombic decay (ICD) is a fundamental non-radiative relaxation mechanism by which an electronically excited atom or molecule embedded in a weakly bound environment transfers excess energy to a neighbour, inducing its ionisation and emitting a low-energy electron. First observed in rare-gas clusters, ICD rapidly redistributes energy across molecular assemblies on femtosecond timescales, generating reactive low-energy electrons that can initiate chemical damage in biological and condensed-phase contexts. The efficiency of ICD depends on the local coordination environment, interatomic distances and competing processes such as proton transfer or Auger–Meitner decay. In aqueous or solvated systems, cascades of ICD and related electron-transfer-mediated decay steps multiply charge and produce clusters of radicals and ions, with implications for radiation chemistry, nanomaterials and medical therapies. Recent advances in coincidence spectroscopy and macroscopic quantum electrodynamics have illuminated the site specificity, environmental influence and potential for external control of ICD, underscoring its global significance in fields ranging from radiobiology to materials science.

Research from Nature Portfolio

Advanced coincidence spectroscopy has revealed the sequence of low-energy-electron–producing steps following core-level ionisation of solvated magnesium ions, confirming predicted interatomic and intermolecular decay cascades and the recurrent recovery of ionic ground states under continuous irradiation. Studies of hydrated aluminium ions have demonstrated two sequential electron-transfer-mediated decay processes, each yielding multiple ionised water molecules and low-energy electrons, thereby amplifying local water ionisation and radical formation. A site-specific comparison of ICD and Auger decay in core-ionised krypton clusters has provided quantitative agreement with theoretical models, verifying that ICD efficiency rises with the number of nearest neighbours and affirming the spatial dependence of decay pathways in atomic clusters.

Interatomic Coulombic Decay in Molecular Systems publication trend

The graph below shows the total number of articles in interatomic coulombic decay in molecular systems across all publications each year (not limited to Nature Index journals).

Technical terms

Interatomic Coulombic Decay (ICD): A non-radiative process in which an excited atom or molecule relaxes by transferring energy to a neighbouring species, causing its ionisation and emission of a low-energy electron.

Electron-Transfer-Mediated Decay (ETMD): A cascade mechanism in which ionisation of one site leads to sequential electron transfer and secondary ionisation events in surrounding molecules.

Low-Energy Electrons (LEEs): Electrons with kinetic energies typically below 20 eV, capable of inducing significant chemical and biological damage through secondary reactions.

Inner-Valence Ionization: Removal of an electron from an inner-valence orbital, creating a vacancy that can trigger ICD or related non-radiative decay pathways.

References

1. X-ray radiation damage cycle of solvated inorganic ions. Nature Communications (2024).
2. Radiation damage by extensive local water ionization from two-step electron-transfer-mediated decay of solvated ions. Nature Chemistry (2023).
3. Damaging Intermolecular Relaxation Processes Initiated by Heavy-Ion Irradiation of Hydrated Biomolecules. Physical Review X (2025).
4. Experimental quantification of site-specific efficiency of Interatomic Coulombic Decay after inner shell ionization. Communications Physics (2023).
5. Competition between proton transfer and intermolecular Coulombic decay in water. Nature Communications (2018).
6. The influence of retardation and dielectric environments on interatomic Coulombic decay. Nature Communications (2018).
7. Autoionization Mediated by Electron Transfer. Physical Review Letters (2011).
8. Intermolecular Coulombic Decay in Liquid Water. Physical Review Letters (2022).
9. Impact of cavity on interatomic Coulombic decay. Nature Communications (2021).