Here Comes The Attosecond

By Roland Piquepaille

Recently, an international team of physicists finally succeeded in breaking the so-called femtosecond barrier. With a complex, high-energy laser, they generated a pulse of light little more than half a femtosecond long -- 650 attoseconds, to be precise.

"This is the real timescale of matter," says Paul Corkum, a physicist with the Steacie Institute for Molecular Sciences in Ottawa and one of the principal investigators in the study. "We're gaining the ability to look at the microworld of atoms and molecules on its own terms."

What are the potential usages of this new unit?

The femtosecond is great for handling whole atoms and molecules. But for the physicist interested in electrons, which are far smaller, lighter, and faster than the atomic nuclei they swarm around, that timescale is just too slow. "We're interested in taking this a step further," says Ferenc Krausz, a principal investigator of the study and a physicist at the Photonics Institute at the Vienna University of Technology.

No sooner had the physicists caught an attosecond pulse than they demonstrated its usefulness. They aimed an attosecond pulse and a longer pulse of red light into a gas of krypton atoms. The attosecond pulse excited the krypton atoms, kicking electrons free; then the red-light pulse hit the electrons and took a reading of their energy. By adjusting the time delay between the two pulses, the scientists gained a very precise measurement