Researchers have used powerful X-ray flashes to watch how a molecule changes after absorbing light, revealing chemical motion with atom-level detail and ultrafast timing.
The study was carried out using the European XFEL, one of the worldโs most advanced X-ray laser facilities. The work shows how scientists can follow both electronic changes and atomic vibrations as they happen inside a molecule within trillionths of a second.
When a molecule absorbs light, its electrons can shift into a higher-energy state. Almost immediately, the molecule may bend, redistribute charge, and convert that electronic energy into vibrations. These processes happen so quickly that ordinary instruments cannot capture them clearly.
To study this ultrafast motion, researchers examined a small molecule called 3-fluoropyridine. The molecule contains both nitrogen and fluorine, which allowed scientists to observe the reaction from two different atomic sites.
First, the researchers used an ultraviolet laser pulse to excite the molecule. This pushed its electrons into a higher-energy arrangement and caused the normally flat molecule to distort. The molecule then passed through a brief transition point known as a conical intersection, where electronic motion and nuclear motion become closely linked.
After this, the molecule returned to its ground state. The energy that had first been stored electronically was converted into molecular vibrations, causing the atoms to move relative to one another.
Using time-resolved X-ray photoelectron spectroscopy, the team sent delayed X-ray pulses into the molecule and removed deeply bound electrons from selected atoms. By measuring the energy of those electrons at different time delays, the researchers reconstructed how the molecule changed over a few picoseconds.
The results showed that different atoms inside the same molecule can reveal different parts of a chemical reaction. The fluorine atom mainly reflected vibrational motion, while the nitrogen atom captured a more complex mixture of charge movement and structural change.
This means that no single atom tells the full story. By observing multiple atomic sites, scientists can separate electronic dynamics from vibrational motion and build a clearer picture of how chemical reactions unfold.
The approach could help researchers study many light-driven processes, including how molecules protect DNA from light damage, how energy moves in solar materials, and how complex molecular systems respond to radiation.
The findings show that advanced X-ray tools can now capture chemistry where it begins: at specific atoms and on the natural timescale of molecular motion.
Journal Reference:
Martรญnez Gutiรฉrrez, A., Alexander, O., Estรฉvez Alonso, P., Paoloni, L., Mullins, T., Al-Haddad, A., Baumann, T. M., Boll, R., Bostedt, C., Dold, S., De Fanis, A., Geloni, G., Ilchen, M., Ismail, I., Lautenschlager, B., Mazza, T., Moonshiram, D., Oberli, S., Peng, D., Pรผttner, R., et al. (2026). Photoinduced Enhancement of Chemical Shift Sensitivity to Local Vibrations. Journal of the American Chemical Society. https://doi.org/10.1021/jacs.6c06538