Collision inside an atom: quantum ion-atom dynamics
Abstract
Rydberg atoms occupy a central role in quantum science; their loosely bound outer electron gives rise to properties that enable quantum information processing1 or the formation of exotic molecular bonds2. Beyond these roles, they have been proposed as a neutral platform for the observation of quantum effects in collisions and reactions of the ionic core with neutral particles3, 4, a long-standing goal of ion-based chemistry and physics. However, all of the experimental results so far could be explained using a classical description of the internuclear motion5. Here we demonstrate cold collisions inside a Rydberg helium atom, achieved by merging helium Rydberg and ground-state helium beams and imaging individual scattering events. We resolve the fully quantum-coherent motion and observe matter-wave diffraction and tunnelling-driven shape resonances down to collision energies of 90 mK. In the case of identical helium nuclei, we demonstrate a new regime of identical-particle Mott interference6, where quantum statistics begin to govern the total scattering cross section. For distinct isotopes, we show the breakdown of the Born-Oppenheimer approximation and benchmark parameter-free, state-of-the-art theory. We directly measure the helium isotope ionization-energy difference to be 15.0 +/- 0.1 K. Our experiments establish Rydberg atoms as a platform for the direct observation of quantum dynamics with a general class of ions, atoms and molecules.
Related
- Modelling Energy Transfer Efficiency in Collision Induced Dissociation and Unfolding Using Molecular Dynamics Simulations
- Unveiling the Collision-Induced Dissociation Pathways of Protonated PO3G Dimer: An Integrated Energy-Resolved MS and Quantum Chemical Study.
- Crossing the 12,000-atom barrier with heterogeneous quantum-classical supercomputing: quantum chemistry of protein-ligand complexes
- Confinement-Driven Transient Coordination Complexes: H2 Dissociation and Quantum Channel Modification in Single-Atom Contacts
- Quantum evolution kernel for molecular machine learning on programmable neutral-atom arrays
BibTeX
@misc{das2026collision,
title = {{Collision inside an atom: quantum ion-atom dynamics}},
author = {Arijit Das and Yufeng Wang and Marcin Welter and Karl Horn and Dawid Dąbrowski and Michał Przybytek and Julia Narevicius and Michał Tomza and Edvardas Narevicius},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18345},
eprint = {2610.18345},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18345},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Collision inside an atom: quantum ion-atom dynamics
AU - Arijit Das
AU - Yufeng Wang
AU - Marcin Welter
AU - Karl Horn
AU - Dawid Dąbrowski
AU - Michał Przybytek
AU - Julia Narevicius
AU - Michał Tomza
AU - Edvardas Narevicius
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18345
UR - https://arxiv.org/abs/2610.18345
AB - Rydberg atoms occupy a central role in quantum science; their loosely bound outer electron gives rise to properties that enable quantum information processing1 or the formation of exotic molecular bonds2. Beyond these roles, they have been proposed as a neutral platform for the observation of quantum effects in collisions and reactions of the ionic core with neutral particles3, 4, a long-standing goal of ion-based chemistry and physics. However, all of the experimental results so far could be explained using a classical description of the internuclear motion5. Here we demonstrate cold collisions inside a Rydberg helium atom, achieved by merging helium Rydberg and ground-state helium beams and imaging individual scattering events. We resolve the fully quantum-coherent motion and observe matter-wave diffraction and tunnelling-driven shape resonances down to collision energies of 90 mK. In the case of identical helium nuclei, we demonstrate a new regime of identical-particle Mott interference6, where quantum statistics begin to govern the total scattering cross section. For distinct isotopes, we show the breakdown of the Born-Oppenheimer approximation and benchmark parameter-free, state-of-the-art theory. We directly measure the helium isotope ionization-energy difference to be 15.0 +/- 0.1 K. Our experiments establish Rydberg atoms as a platform for the direct observation of quantum dynamics with a general class of ions, atoms and molecules.
ER -