This illustration shows an optical laser pulse (red) and an X-ray laser pulse (light blue) striking a sample. The use of synchronized laser pulses in the same experiment, known as the “pump-probe” technique, is common for SLAC’s Linac Coherent Light Source X-ray laser, and a timing tool developed by an international team allows more precise measurements of the arrival time of laser pulses at LCLS. Credit: Greg Stewart / SLAC National Accelerator Laboratory

This diagram shows the path of X-ray pulses (blue) and pulses from a separate laser (red) and a sequence of measurement tools that provide a highly accurate gauge of the arrival times of each laser. Credit: Nature Photonics

New X-ray tool proves timing is everything

February 20, 2013 by Glenn Roberts Jr.

(Phys.org)—With SLAC’s Linac Coherent Light Source X-ray laser, timing is everything. Its pulses are designed to explore atomic-scale processes that are measured in femtoseconds, or quadrillionths of a second. Determining the instant in time at which the laser strikes a sample, either by itself or in concert with another laser pulse, can be vital to the success of an experiment.

In the Feb. 17 issue of Nature Photonics, researchers detail a new set of tools that better pinpoints the arrival time of X-ray and other laser pulses to within a few femtoseconds of accuracy.

“The development of such a timing tool as well as the demonstration of a few-femtosecond time resolution is opening a large field of applications in trying to resolve ultrafast dynamics in physics, chemistry and biology,” said Marion Harmand of the German Electron Synchrotron (DESY) in Hamburg, Germany, the paper’s lead author.

Many LCLS experiments rely on conventional laser systems, known as optical lasers, that excite and prepare samples in the instant before they are struck by the ultrabright, ultrafast X-ray laser pulses. These experiments are often referred to as “pump-probe.” The optical laser pulse “pumps” the sample to a desired state, and the X-ray laser pulses serve as a high-resolution “probe” of the sample’s properties at the molecular scale.

Read more: New X-ray tool proves timing is everything — phys.org.

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