Roland Piquepaille's Technology Trends
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mercredi 11 juin 2003
 

Before going further, what is an attosecond? It's 10-18 second or just a billionth of a billionth of a second. This article from DISCOVER says that researchers reached this new limit in time using high-energy laser pulses. Here are some excerpts.

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 measurementówithin a matter of attosecondsóof how long it takes the electron to decay. Never before had electron dynamics been studied on so short a timescale.

Here is an illustration showing the attosecond pulse generation and detection, from the Max Planck Institute for Quantum Optics.

Attosecond pulse generation and detection

But obviously, these physicists are not yet satisfied and want to go further.

Of course, one day, perhaps not so very far in the future, even the speedy attosecond will fail to satisfy. Electrons will look downright poky. "As you go into smaller structures of matter, inside the atomic nucleus, processes become even faster," Krausz says. "In nuclear physics, the natural timescale is several orders of magnitude faster -- in the realm of zeptoseconds," or sextillionths of a second.

Please read the full article for more details, illustrations, and related websites

Source: Alan Burdick, DISCOVER Vol. 24 No. 6 (June 2003)


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