ULTRAFAST PROBE

USING NEWLY DEVELOPED ultrafast laser methods, researchers in Austria and Germany have probed inner-shell electronic rearrangements in atoms in real time. The study may allow scientists to follow electron dynamics in chemical reactions with unprecedented time resolution. Molecular vibrations and chemical reaction dynamics are commonly studied using femtosecond (10 -15 second) pumpprobe laser techniques. A short burst of visible or near-IR light pumps a specimen to an excited state; then, a precisely delayed follow-up pulse probes the evolution of the excited species. A series of molecular snapshots can be prepared by varying the delay between the pump and the probe pulses. But inner-shell electron shuffling takes place on an even faster timescale, so shorter bursts of light are needed to interrogate those processes. Using attosecond (10 -18 second) laser methods developed in their laboratory, Vienna University of Technology's Ferenc Krausz, Reinhard Kienberger, and Michael Hentschel; Markus Drescher, of the University of Bielefeld, in Germany; and coworkers ...