Scientists at the European XFEL have watched energy travel through a molecule in real time, tracking how individual atoms respond to light in trillionths of a second, a first for chemistry at this scale.
Using rapid X-ray flashes at the European XFEL facility, researchers studied 3-fluoropyridine, a ring-shaped molecule containing nitrogen and fluorine. When hit by an ultraviolet laser pulse, the molecule absorbed energy and bent out of its normally flat shape. As it passed through a fleeting crossing point called a conical intersection where electronic and structural motion become tightly coupled. The X-ray pulses captured something no one had seen before: individual atoms recording completely different stages of the same transformation [1].
The fluorine atom served as a marker of how the molecule's vibrations relaxed over time, while the nitrogen atom, which played a direct role in the electronic excitation, reflected both electron redistribution and structural change simultaneously. The technique opens a new window into light-driven chemistry with potential implications for understanding how DNA withstands light exposure and how energy moves through solar materials.