Stanford scientists, along with an international team at the German particle
lab DESY's free electron laser, have managed to observe exploding polystyrene
beads on a femtosecond timescale and 10 nm lengthscale, using equipment not
much more sophisticated than a dusty mirror.
The new technique, which produces a "hologram" of the object after excitation,
could prove useful for X-ray free-electron lasers (XFELs). These lasers will
allow users to fire photon pulses with short wavelengths and short duration,
probing structure at and below the nanometer scale. However, the excitation
pulse would destroy the object, and the achievable image resolution depends
critically on how fast the destruction occurs. Using the dusty-mirror method,
it is possible to excite and observe an object with the same pulse of light, to
measure the dynamics of the XFEL interaction with an inherently fine time
resolution that does not require sophisticated synchronization techniques.
The scientists observed 140-nm polystyrene spheres arrayed on a silicon nitride
membrane, which was positioned in front of an X-ray mirror. As the beam hit the
spheres the first time, it started an explosion. The beam bounced off the
mirror and through the expanding spheres a second time, collecting an image
shortly after the first pulse. Both beams were directed onto a CCD. The
resulting pattern of concentric rings, produced by the two interfering waves,
was modulated with speckles that contained information about the exploding
spheres.
H. N. Chapman, S. P. Hau-Riege, M. J. Bogan, S. Bajt, A. Barty, S. Boutet, S.
Marchesini, M. Frank, B. W. Woods, W. H. Benner, R. A. London, U. Rohner, A.
Szöke, E. Spiller, T. Möller, C. Bostedt, D. A. Shapiro, M. Kuhlmann, R.
Treusch, E. Plönjes, F. Burmeister, M. Bergh, C. Caleman, G. Huldt, M. M.
Seibert and J. Hajdu, "Femtosecond Time-Delay X-ray Holography",
Nature 448, 676 (2007)
To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/holography07.html
