The world’s most intense X-ray laser may soon be the fastest strobe-light camera ever. Two of the laser’s first experiments show the device will be able to take snapshots of single molecules in motion — without destroying them first.
The laser, called the Linac Coherent Light Source, takes up a third of the two-mile-long linear accelerator at the SLAC National Accelerator Lab in Menlo Park, California. In the accelerator hall, tight bunches of electrons wriggle through a series of magnets and give off X-rays billions of times brighter than earlier X-ray sources could muster. The wavelength of these X-rays is comparable to the radius of a hydrogen atom — about one angstrom, or one ten-billionth of a meter — and each pulse can be as short as a few quadrillionths of a second.
These features make this kind of X-ray, called a hard X-ray for its ability to penetrate matter, an ideal scalpel to probe the inner workings of atoms and molecules. When the laser first flashed in April 2009, physicists dreamed of using it to make 3-D, time-lapse movies of atomic bonds breaking and proteins changing shape. Just like stop-motion photographs showed 19th-century photographers how horses run, the X-ray laser should show modern scientists how atoms interact.
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