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World's shortest light pulse helps scientists slow things down

A femtosecond is an unbelievably brief instant in time. It is a quadrillionth of a second; there are as many femtoseconds in one second as there are seconds in 30 million years.

Earlier this month, International Business Machines Corporation scientists announced that they had generated the world's shortest light pulses, just 12 femtoseconds (fs) in length. Equally important, the device that they have invented (they call it a ''light compressor'') can produce 800 of these briefest-of-brief flashes per second.

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The IBM scientists - Jean-Marc Halbout and Daniel Grischkowsky - developed the light compressor to study the kinetics of chemical reactions and other physical processes which take place at the atomic level.

The device can act as a strobe to illuminate the dynamics of processes that involve large numbers of previously unseen and unmeasured events, the scientists suggest.

Mr. Halbout and Mr. Grischkowsky were able to shave 4 femtoseconds off the previous 16-fs record reported this summer by scientists at the Massachusetts Institute of Technology.

The MIT scientists, in turn, had broken the 30-fs record set by Richard Fork, Charles Shank, Richard Yen, Roger Stolen, and William Tomlinson of American Telephone & Telegraph Bell Laboratories two years ago.

An example of one way this new capability can be used comes from Bell Labs. There, Michael Downer, Mr. Fork, and Mr. Shank have employed an 80-fs pulsed laser to produce the slowest of slow-motion movies. This details the melting of the surface of a silicon crystal after it is struck by the laser pulse.

The actual time elapsed during their film is a mere billionth of a second.

Just as aircraft design is driven by engine technology, so scientific progress depends in large part on the precision of its instruments. Thus, the ability to record and measure events in the femtosecond range will undoubtedly lead to significant new scientific insights.

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