A team at the University of California used picosecond x-ray diffraction to measure the response of GaAs crystal to sudden heating. This could advance efforts to monitor changes in electron density during biological and chemical reactions with femtosecond resolution. A lidar image of the Bainbridge Island scarp shows the ridge that runs through the upper portion of the land mass. Courtesy of Kitsap Public Utilities District.For years, researchers have used x-ray diffraction in the form of synchrotron radiation and conventional electron-impact sources to uncover information about the static structure of materials. Often these experiments took place in very large facilities with costly equipment. Now a team led by Christoph Rose-Petruck has re-created a similar effect using a tabletop picosecond x-ray source. A Ti:sapphire laser producing 30-fs pulses simultaneously heats and tests a GaAs wafer. A beamsplitter diverts a portion of the beam to heat the wafer, while the other part of the beam irradiates a copper wire to create picosecond x-ray pulses. Details of the work appear in the March 25 issue of Nature.