First ever tabletop X-ray laser will image the nanoworld
To create an X-ray laser, you usually need a synchrotron - a particle accelerator most-often housed in billion-dollar facilities the size of a football field. But a team of international scientists has created the first coherent X-ray beam that comes from a setup that fits on a laboratory table.
This more manageable device promises to open doors into phenomena on the smallest scales in the natural world.
"It definitely opens up the possibility to probe the shortest space and time scales relevant to any process in our natural world other than nuclear or fundamental particle interactions," said Henry Kapteyn of JILA at the University of Colorado at Boulder.
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Because X-rays have very short wavelengths, they could be used to image individual interactions of molecules or to view the smallest components of organisms, reports the Los Angeles Times.
The team used a decades-old technique called high-harmonic generation, which directs intense pulses of infrared light into a spray of gas. But they pushed it to its limit by using extremely short bursts of infrared light. The beam that comes out of the gas includes all wavelengths of the original laser, but has added wavelengths in the ultraviolet region of the spectrum, which are created when the laser ionizes the gas atoms.
"Just as a violin or guitar string will emit harmonics of its fundamental sound tone when plucked strongly, an atom can also emit harmonics of light when plucked violently by a laser pulse," adds Murnane. "The laser pulse first plucks electrons from the atoms, before driving them back again where they can collide with the atoms from which they came. Any excess energy is emitted as high-energy ultraviolet photons."
The result is an X-ray burst that can follow the tiniest and fastest physical process in nature, including the coupling of electrons and ions in molecules undergoing chemical reactions, or the flow of charges and spins in materials.
The beams generated by the device could, for instance, help materials scientists to make better solar materials by tracking the paths of electrons through solar cells, and might allow chemists to trace the ultrafast dynamics of photosynthesis and catalysis, according to Nature.
"Thirty years ago, people were saying we could make a coherent X-ray source, but it would have to be an X-ray laser, and we would need an atomic bomb as an energy source to pump it," said Deborah Jackson, a program officer at the National Science Foundation, which funded the research. "Now, we have these guys who understand the science fundamentals well enough to introduce new tricks for efficiently extracting energetic photons, pulling them out at X-ray wavelengths ... and it's all done on a table-top."
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