Atomic X-ray Laser Blasts Ahead

A femtosecond-pulsed, atomic X-ray laser—beaming at the highest energies reached so far by its kind—could enable new developments in high-resolution spectroscopy, according to a report in Nature (DOI: 10.1038/nature10721). X-ray lasers have been in use since the 1980s, but scientists are forever in search of higher energy, shorter-pulsed, and more coherent beams to probe the atomic-scale distances and motions of molecules. Nina Rohringer of the Center for Free-Electron Laser Science, in Germany, and colleagues used SLAC National Accelerator Laboratory’sLinac Coherent Light Source (LCLS), which is a free-electron laser, to pump collections of neon atoms into high-energy states and achieve laser radiation of 849 eV. Although this energy is actually less than the 960 eV produced by LCLS, which is currently the world’s most powerful X-ray laser, the light produced by an atomic laser has advantages over that of a free-electron laser. For example, the Rohringer group’s laser produces light that is far more coherent, with photon energy spreads of less than 1 eV, whereas LCLS’s spread averages 15 eV.