Scientists Watch Chemistry Unfold Atom by Atom

Researchers at the European XFEL have achieved a new milestone in observing chemical reactions in real time. By tracking the molecule 3-fluoropyridine, the team successfully monitored how atoms behave during light-driven changes at a scale of trillionths of a second.

Traditional methods often struggle to distinguish between the movement of electrons and the physical vibration of a molecular structure. This study demonstrates that different atoms within the same molecule provide distinct signals. Nitrogen atoms tracked the redistribution of electric charge while fluorine atoms signaled the vibrations of the structure.

To accomplish this, the team used time-resolved X-ray photoelectron spectroscopy. They hit the molecule with an ultraviolet laser pulse to trigger a reaction, followed by an X-ray pulse to capture snapshots of the nitrogen or fluorine atoms at specific delays. These measurements were then mapped against simulations to create a sequence of the atomic transitions.

The findings offer a new path for studying light-harvesting materials and the biological mechanisms that protect DNA from solar radiation. By observing these changes at the atomic level, scientists can now piece together the sequence of events that follow light absorption with much greater precision.

This method is applicable beyond the test molecule used in this study. It provides a new tool for examining functional organic materials and biomolecular components, helping researchers understand the fundamental mechanics of photochemistry at the speed at which they occur.