Author(s): Kilian P. Heeg, Johann Haber, Daniel Schumacher, Lars Bocklage, Hans-Christian Wille, Kai S. Schulze, Robert Loetzsch, Ingo Uschmann, Gerhard G. Paulus, Rudolf Rüffer, Ralf Röhlsberger, and Jörg Evers
Slow light effects have been measured for x rays using a cavity filled with iron nuclei, where the speed of light was reduced by a factor of 10,000.
[Phys. Rev. Lett. 114, 203601] Published Mon May 18, 2015