Scientists have uncovered the hidden cause of radiation sickness by photographing atoms ‘walking around’ before exploding.
- process: This research focuses on electron transfer-mediated decay (ETMD), a radiation-driven process that breaks apart loosely bonded atoms. This mechanism is particularly important because it can generate highly reactive particles in water and is an important factor in the effects of radiation on biological systems.
- experiment: Scientists tracked this process in amazing detail using special reaction microscopy combined with advanced theoretical simulations. This allows us to precisely track how damping evolves over time in carefully controlled model systems.
- What they discovered: The team effectively created a real-time “video” of atoms moving around each other for up to picoseconds until the system eventually fell apart. This reveals dynamic and ever-changing processes rather than simple, static events.
- Why it’s important: These findings provide a clearer picture of how radiation damage progresses at the atomic level. A deeper understanding of this process could allow researchers to improve models of the effects of radiation in biological environments and potentially guide future protection strategies.
How radiation damages cells at the atomic level
High-energy radiation, such as X-rays, can harm living cells by disrupting atoms and molecules. When this happens, those particles become excited and often break down, destroying important biomolecules and potentially disrupting larger biological systems. Different types of decay processes can occur, and scientists are studying them closely to better understand how radiation causes damage and how it can be mitigated.
In a new study, researchers from the Department of Molecular Physics and international collaborators focused on a specific radiation-driven process called electron transfer-mediated decay (ETMD). In this process, radiation first excites atoms. That atom then stabilizes itself by pulling electrons from nearby atoms, and the released energy ionizes its third neighbor. The research team was able to directly observe how the atoms in the model system move and reorganize before this unusual collapse occurs. Their results provide the most detailed real-space and real-time view of ETMD to date.
Track the movement of atoms in real time
To investigate this process, the scientists used a simple model system consisting of one neon atom (NeKr2 trimer) weakly bound to two krypton atoms. After knocking electrons out of neon atoms using soft X-rays, they tracked how the system evolved down to picoseconds, a very long time on the atomic time scale, before collapse occurred. During this time, electrons moved between atoms and lower energy electrons were released.
The researchers used the latest COLTRIMS reaction microscopes at the synchrotron radiation facilities BESSY II (Berlin) and PETRA III (Hamburg) to reconstruct the exact arrangement of the atoms at the moment the decay occurred. They combined these measurements with detailed ab initio simulations that tracked thousands of possible atomic paths and calculated the likelihood of decay occurring along each path.
Atoms on the Move “Movie”
The results revealed something unexpected. The atoms were not fixed in place. Instead, they moved in a wandering pattern, constantly changing positions and reshaping the structure of the system. This move had a significant impact on both the timing and outcome of the decay.
“We can literally observe how the atoms move before the collapse occurs,” says Florian Triinter, one of the first authors. “Collapse is not just an electronic process, but is induced by nuclear motion in a very direct and intuitive way.”
This study shows that ETMD does not arise from a single stable structure. Different arrangements prevail at different moments. At the initial stage, a decay close to the original configuration occurs. Then, one krypton atom approaches the neon atom, while the other krypton atom moves away, creating favorable conditions for electron transfer and energy flow. At a later stage, the atoms become more elongated and form a distorted shape, reflecting a wobbling motion. These changes result in significant changes in the damping rate depending on the geometry.
“The atoms explore a large region of configuration space before finally collapsing,” explains Till Jahnke, senior author of the study. “This shows that nuclear motion is not just a minor modification, but fundamentally controls the efficiency of nonlocal electron decay.”
Why is it important to understand ETMD?
ETMD is of increasing interest because it produces low-energy electrons that can cause chemical damage to liquids and biological materials. Knowing how this process depends on the arrangement and motion of atoms is essential for accurately modeling radiation damage in water and biological environments and for interpreting ultrafast X-ray experiments. The results also support the development of theoretical models that can apply these insights to larger and more complex systems.
This study provides a foundation for extending these ideas to liquids, solvated ions, and biological systems by providing an accurate benchmark for the simplest ETMD-enabled system containing three atoms.
“This study shows how nonlocal electron decay can be used as a powerful probe of molecular motion,” the authors conclude. “This opens the door to imaging ultrafast dynamics in weakly coupled materials in unprecedented detail.”
