Physicists Create First Atomic X-Ray Laser – 'Purest' Beam Ever Will Probe Molecular Mysteries

first atomic x-ray laser - artist conception
Artist's conception of the new atomic hard X-ray laser (Illustration by Gregory M. Stewart)

In creating the shortest (fastest) and “purest” x-ray laser pulses ever achieved, scientists working at the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory, in Menlo Park, California,  have fulfilled a 1967 prediction that atomic scale x-ray laser could be made in the same manner as visible-light lasers.

With the help of SLAC’s Linac Coherent Light Source (LCLS), researchers aimed the powerful x-ray source beam — billions of times brighter than any previous  source — at a capsule of neon gas, triggering a prodigious output of x-ray emissions…and voila!…the world’s first atomic x-ray laser was born.

The major technological achievement, which was not possible before the LCLS was developed, will allow real-time probing of chemical reactions and biological molecules at work — sub-cellular activity normally too tiny and too quick to be observed by microscopic techniques currently in use.

“The shorter the pulses, the faster the changes we can capture. And the purer the light, the sharper the details we can see,” said physicist Nina Rohringer, who led the research.  “X-rays give us a penetrating view into the world of atoms and molecules.”

Rohringer is a group leader at the Max Planck Society’s Advanced Study Group in Hamburg, Germany, which collaborated with researchers from SLAC and Colorado State University.

How the Atomic X-Ray Laser Works

The neon-based, atomic x-ray laser’s light is much more “pure” that the   brighter and more powerful x-ray pulses of the LCLS laser, but to produce a beam of its purity requires the brute force of the larger laser.

The LCLS laser “induces” electrons in the neon atoms to rapidly shift from higher to lower orbits, or shells, within the neon atom, which then triggers the emission of photons of a single color (frequency) in the ultra-short wave length range that characterize x-rays. This photon reaction only occurs in 1 out of 50 such electron shifts, but the rate of x-ray pulses is fast enough to insure sufficient photons are emitted to impact neighboring neon atoms and thus trigger the run-away reaction — amplifying the laser beam 200 million times!

first atomic x-ray laser - artist conception
A powerful X-ray laser pulse from SLAC National Accelerator Laboratory's Linac Coherent Light Source comes up from the lower-left corner (shown as green) and hits a neon atom (center). This intense incoming light energizes an electron from an inner orbit (or shell) closest to the neon nucleus (center, brown), knocking it totally out of the atom (upper-left, foreground). In some cases, an outer electron will drop down into the vacated inner orbit (orange starburst near the nucleus) and release a short-wavelength, high-energy (i.e., "hard") X-ray photon of a specific wavelength (energy/color) (shown as yellow light heading out from the atom to the upper right along with the larger, green LCLS light). X-rays made in this manner then stimulate other energized neon atoms to do the same, creating a chain-reaction avalanche of pure X-ray laser light amplified by a factor of 200 million.

{See the inset photo description for more details of how this laser was created]

The end result is a highly purified laser beam that will enable researchers to illuminate and distinguish details of ultrafast reactions that had been impossible to see before.

“This achievement opens the door for a new realm of X-ray capabilities,” said John Bozek, LCLS instrument scientist. The researchers envision a powerful, coupled system in which the first pulse creates a change in the study sample , and the second laser pulse records any changes with unmatched precision — up to a quadrillionth of a second in duration.

Rohringer  and her team are planning on creating even shorter-pulsed, higher-energy atomic X-ray lasers using oxygen, nitrogen or sulfur gas.

In a related development, researchers at the same SLAC National Accelerator Laboratory, using the LCLS laser, fired an x-ray beam at a sample of aluminum, heating it to 3.6 million degrees (hotter than the sun’s corona) and then creating a type of plasma known as hot dense matter. Check out the Wired blog post for more.

The atomic x-ray laser researchers reported their results today in the journal Nature. Additional authors include Richard London, Felicie Albert, James Dunn, Randal Hill and Stefan P. Hau-Riege from Lawrence Livermore National Laboratory (LLNL); Duncan Ryan, Michael Purvis and Jorge J. Rocca from Colorado State University; and Christoph Bostedt from SLAC.

Image Credit: Illustration by Gregory M. Stewart, SLAC National Accelerator Laboratory

The work was supported by Lawrence Livermore National Laboratory’s Laboratory Directed Research and Development Program. Authors Roca, Purvis and Ryan were supported by the DOE Office of Science. LCLS is a national scientific user facility operated by SLAC and supported by DOE’s Office of Science.
SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science. To learn more, please visit www.slac.stanford.edu.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.


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