Single-shot x-ray diffraction aims at imaging macromolecules

A few years ago, researchers at Uppsala University (Uppsala, Sweden) predicted that ultrashort, high-intensity x-ray pulses from free-electron lasers could allow diffractive imaging of single biological molecules.1 The idea was to take advantage of the mass inertia of atomic constituents against kinetic disintegration during the build-up of Coulomb potential by ionization. Now an international working group based at Deutsches Elektronen-Synchrotron (DESY; Hamburg, Germany), which includes the Uppsala team and a team from Lawrence Livermore National Laboratory (Livermore, CA), has investigated that prediction experimentally, using DESY's recently completed soft-x-ray gigawatt free-electron laser (see www.laserfocusworld.com/articles/245104).2,3 As a first test at a 32 nm wavelength, a single micrometer-size pattern cut through a 20 nm silicon nitride membrane was used as the scattering object (rather than a molecule, which is the ultimate goal), just to show that a diffraction pattern can be obtained from such a structure before it disintegrates, and that the diffraction pattern can be evaluated uniquely to reconstruct the object's structure.