The shortest, purest x-ray laser pulses ever achieved were created, fulfilling a 45-year-old prediction and opening the door to new medicines, materials and devices. Stanford Linear Accelerator Center scientists created the pulses by aiming its Linac Coherent Light Source at a capsule of neon gas, setting off an avalanche of x-ray emissions to create the world’s first “atomic x-ray laser.” Their findings appeared in the Jan. 26 issue of Nature. “X-rays give us a penetrating view into the world of atoms and molecules,” said physicist Nina Rohringer, who led the research. She collaborated with scientists from SLAC, Lawrence Livermore National Laboratory and Colorado State University. A powerful x-ray laser pulse from SLAC National Accelerator Laboratory's Linac Coherent Light Source comes up from the lower-left corner (green) and hits a neon atom (center). (Illustration: Gregory M. Stewart/SLAC) The new laser fulfills a 1967 prediction that x-ray lasers could be made by first removing inner electrons from atoms and then inducing electrons to fall from higher to lower energy levels, releasing a single color of light in the process. But until 2009, when LCLS turned on, no x-ray source was powerful enough to create this type of laser. To make the atom laser, LCLS’s powerful x-ray pulses — each a billion times brighter than any available before — knocked electrons out of the inner shells of many of the neon atoms in the capsule. When other electrons fell in to fill the holes, about one in 50 atoms responded by emitting a photon in the hard x-ray range, which has a very short wavelength. Those x-rays then stimulated neighboring neon atoms to emit more x-rays, creating a domino effect that amplified the laser light 200 million times. “This work presents a big advance in the quest for shorter-wavelength lasers,” said Rich London, a LLNL scientist. “In addition, the demonstration of the neon x-ray laser provides a very sensitive test of the physics of intense x-ray interaction with atoms. By comparing theoretical modeling to the observed output signals, one can pin down the basic ultrafast processes occurring in the region where the LCLS beam interacts with the gas.” Next, Rohringer says she will try to create even shorter-pulse, higher-energy atomic x-ray lasers using oxygen, nitrogen or sulfur gases. For more information, visit: www.llnl.gov