DOE Pulse
  • Number 316  |
  • July 19, 2010

Unpeeling atoms and molecules from the inside out

First experiments at SLAC's Linac Coherent Light Source stripped electrons one by one from neon atoms. Credit: Gregory Stewart, SLAC.

First experiments at SLAC's Linac
Coherent Light Source stripped
electrons one by one from neon
atoms. Credit: Gregory Stewart, SLAC.

The first published scientific results from the world's most powerful hard X-ray laser, located at DOE's SLAC National Accelerator Laboratory, show its unique ability to control the behaviors of individual electrons within simple atoms and molecules by stripping them away, one by one—in some cases creating hollow atoms.

These early results describe in great detail how the Linac Coherent Light Source's intense pulses of X-ray light change the very atoms and molecules they are designed to image. Controlling those changes will be critical to achieving the atomic-scale images of biological molecules and movies of chemical processes that the LCLS is designed to produce.

In a report published in the July 1 issue of Nature, a team led by Argonne National Laboratory physicist Linda Young describes how they were able to tune LCLS pulses to selectively strip electrons, one by one, from atoms of neon gas. By varying the photon energies of the pulses, they could do it from the outside in or—a more difficult task—from the inside out, creating so-called "hollow atoms."

"Until very recently, few believed that a free-electron X-ray laser was even possible in principle, let alone capable of being used with this precision," said William Brinkman, director of DOE's Office of Science. "That's what makes these results so exciting."

In another report, published June 22 in Physical Review Letters, a team led by physicist Nora Berrah of Western Michigan University—the third group to conduct experiments at the LCLS—describes the first experiments on molecules. Her group also created hollow atoms, in this case within molecules of nitrogen gas, and found surprising differences in the way short and long laser pulses of exactly the same energies stripped and damaged the nitrogen molecules.

"We just introduced molecules into the chamber and looked at what was coming out there, and we found surprising new science," said Matthias Hoener, a postdoctoral researcher in Berrah's group at WMU and visiting scientist at Lawrence Berkeley National Laboratory who was first author of the paper. "Now we know that by reducing the pulse length, the interaction with the molecule becomes less violent."

While the first experiments were designed to see what the LCLS can do and how its ultra-fast, ultra-bright pulses interact with atoms and molecules, they also pave the way for more complex experiments to come. Its unique capabilities make the LCLS a powerful tool for research in a wide range of fields, including physics, chemistry, biology, materials and energy sciences. Read more…

[Glennda Chui, 650-926-4897,]