Surprising Discovery Contradicts Predictions
What happens when you focus X-ray beams a billion times stronger than the sun’s brightness on a spot 100 times smaller than a human hair? A startling discovery that could lead the way to engineering better materials.
That, and it’s just cool, said UNL physicist Matthias Fuchs, who led the project.
“Discovering something unexpected is always extremely interesting for physicists,” Fuchs said. “This opens a whole new realm of physics.”
He and his colleagues smashed X-ray photons into a metal foil to observe a fundamental process whereby two photons that simultaneously hit an atom are converted into a single higher-energy photon, and an atomic electron is ejected.
The process is extremely rare. Observing it requires an X-ray laser so enormous that only two exist in the world. The team used the LCLS X-ray free-electron laser at the U.S. Department of Energy’s SLAC National Accelerator Laboratory at Stanford University.
What they observed contradicts theoretical predictions that have stood for 60 years – the energy of the generated photon was significantly lower than expected.
It appears the X-rays interact with the entire atom and not just the atomic electron as predicted, Fuchs said. He continues to investigate the surprising results.
The newly observed process has the potential to provide important clues about both the material’s composition and arrangement with atomic spatial resolution.
“This opens a whole new realm of physics.”
“This would give you much more information about the material so you can engineer its properties much better,” Fuchs said. “But right now we are at the very fundamental stage of trying to understand the physics behind the process.”
The research, funded by DOE, was published in the journal Nature Physics. Fuchs won an Air Force Office of Scientific Research Young Investigator Award in 2015 to further his next-generation X-ray research.
His collaborators are at the Stanford Linear Accelerator Center, Stanford University and Bar-Ilan University in Israel.
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