Researchers have made an X-ray beam travel 10,000 times slower than the speed of light — an effect seen before only for visible light.

Physicists have previously slowed light waves to a crawl and even stopped them by controlling the transparency of the medium through which the light passed — usually an ultracold gas of atoms such as sodium. They did this by tuning the interaction of light with the electrons in the gas. Now, a team led by Jörg Evers of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, has seen a similar effect by letting X-rays from a synchrotron interact with the nuclei of iron atoms, rather than with their electrons.

Controlling X-rays in this way could be useful for high-resolution imaging and other applications.

Phys. Rev. Lett. http://dx.doi.org/10.1103/physrevlett.114.203601 (2015)