November 29, 2001	Thursday	Ramazan 13, 1422

PARIS, Nov 28: Austrian scientists say they have developed the world’s fastest laser, a device that opens the door to studying the movement of electrons and other atomic processes.

The laser works at 650 attoseconds (650 million trillionths of a second), a team led by Ferenc Hausz of Vienna’s Technical University say in the British science weekly Nature out on Thursday.

It marks a giant step forward in ultra-lasers, a field in which scientists strive to find exactly how a chemical or physical reaction works in order to develop new materials and drugs.

The achievement heralds “the dawn of attophysics,” said Yaron Silberberg of the Weizmann Institute of Science in Israel, referring to an attosecond, the shortest unit of time for which we currently have a name.

An attosecond is to a second what a second is to 32 billion years.

“At these timescales, chemistry is essentially frozen in time,” Silberberg said, hoping that enhancements could one day yield a laser to show how molecules gain and shed electrons themselves.

The laser first shines a pulse onto a gas of neon atoms. This splits the beam into an optical pulse and a “harmonic” pulse in the ultraviolet and X-ray ranges of the energy spectrum.

The two beams then pass through a zirconium filter, which causes the harmonic pulse to slow down but does not affect the speed of the optical pulse.

By directing the two beams at a cloud of krypton gas atoms, the scientists were able to measure the difference in time between when the atoms were hit by the harmonic pulse and when they were hit by the optical pulse.

That enabled them to monitor the spectrum of energy released by electrons as they were expelled from the atoms.

The attosecond laser builds on the femtosecond laser, a device which is fractionally slower and already used to study chemical reactions.

Femtochemistry leapt to prominence in 1999 when Ahmed Zewail of Egypt won the Nobel Prize for Chemistry for his work in the field.

A femtosecond is 10 to the power of minus 15, while an attosecond is 10 to the power of minus 18.—AFP