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Research Published in Nature Communications

First direct look at how light excites electrons to kick off a chemical reaction
Graphic showing light hitting a ring-shaped molecule called CHD.

Researchers involving Dr Adam Kirrander in the School of Chemistry at the University of Edinburgh together with collaborators at Brown and SLAC have achieved the first direct observation of an excited electronic state in a molecule.

The scientists have observed how a molecule absorbs light energy. The experiments have the potential to improve the efficiency of devices that use sunlight to produce electricity or aid the design of new molecules that use light to treat cancer. The achievement is a major development of x-ray diffraction, an experimental technique that has existed for 100 years and has revealed the shape of important proteins and the DNA double-helix, leading to multiple Nobel Prizes. Using an X-ray Free-Electron Laser, the international team consisting of scientists from Brown and Edinburgh Universities and the Stanford National Accelerator Laboratory were able to directly observe the fast rearrangement of electrons inside a molecule, in a major breakthrough published in Nature Communications.

Light-driven reactions are at the heart of human vision, photosynthesis and solar power generation. Seeing the very first step opens the door to observing chemical bonds forming and breaking. The team used an X-ray free-electron laser at SLAC to make a ‘molecular movie’ of light hitting a ring-shaped molecule called CHD. Within 30 femtoseconds, or millionths of a billionth of a second, clouds of electrons deformed into larger, more diffuse clouds corresponding to an excited electronic state.

X-ray scattering has been used to determine the structure of matter for more than 100 years, but this is the first time the electronic structure of an excited state has been directly observed.

Dr Adam Kirrander

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Friday, May 1, 2020