Number 294 (Story #2), November 6, 1996 by Phillip F. Schewe and Ben Stein THE SHORTEST X-RAY PULSES yet produced have been made at LBL by shooting 100-femtosecond bursts of infrared laser light at right angles into a beam of electrons. Some of the photons are converted into x rays by scattering (through 90 degrees) into the same direction as the electrons. The resultant x-ray bursts are themselves short---about 300 fsec---and potent, with an energy of 30 keV (or, equivalently, a wavelength of 0.4 angstroms). By narrowing the electron beam further (currently it is a mere 90 microns wide), even sharper x-ray pulses (50 fsec) are in the offing. Theses pulses are ideal probes---their small wavelength permits studies of atomic structure with high resolution. Meanwhile their short duration make them an excellent strobe light for glimpsing ultrafast phenomena. For example, the LBL researchers are using the x-ray pulses to study the melting of silicon. (R.W. Schoenlein et al., Science, 11 October 1996.)