Ultrafast X-ray flashes map light-driven chemical changes atom by atom
Researchers used femtosecond X-ray pulses at the European XFEL to watch how a molecule redistributes energy after absorbing UV light, revealing distinct atomic responses.
At the Small Quantum Systems instrument of the European XFEL, scientists examined the light-induced dynamics of 3-fluoropyridine using time-resolved X-ray photoelectron spectroscopy. After a brief UV laser pulse excited the molecule, a series of precisely delayed soft-X-ray pulses ionized either the nitrogen or fluorine atoms, allowing the team to record changes in the emitted electron energies. The data revealed that the fluorine atom served as a clear marker of vibrational energy dissipation, whereas the nitrogen atom provided a more complex signal that combined electronic redistribution and structural deformation.
The experiment captured the passage through a conical intersection, a fleeting state where electronic and nuclear motions become strongly coupled. Computational modeling linked the observed spectra to underlying electronic and geometric transformations. The approach opens a pathway to study increasingly complex systems, from functional organic compounds to biomolecular building blocks, with atomic-site specificity and femtosecond resolution.
Why it matters
Understanding how light energy moves within molecules can guide the design of better solar materials and protect biological systems from UV damage.
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