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Scientists break the speed barrier to nab elusive atoms and electrons

WASHINGTON—Scientists are learning to observe and control the incredibly rapid behavior of molecules, atoms and even the electrons inside atoms—the fundamental building blocks of all things living or dead.

Using a high-tech version of stop-action cameras, they say their ultra-fast systems offer the promise of new devices, materials, fuels and medicines for the 21st century.

To do this, physicists have found ways to create extremely short flashes of laser light, which they can use like strobe lamps to "freeze" atomic motions. It's like photographing a 100-mph baseball as it nears home plate, only a billion billion (or a quintillion) times faster.

"We are opening a new field of science," Ray Orbach, the director of the Office of Science at the Department of Energy, told the House Science Committee in April. "Just ask the pharmaceutical industry what they could do with a machine that shows them how the chemical bond forms DURING a chemical reaction."

Orbach was referring to the fact that an atom consists of a nucleus with one or more electrons whirling around it. Atoms "bond" by linking their electrons to construct a molecule, such as water (H2O) or carbon dioxide (CO2). Scientists expect that the new technology will let them watch the clouds of electrons that glue atoms together shift and flow as they form molecules.

With these new tools, chemists hope—among other things—to solve the mystery of exactly how plants soak up the light from the sun and convert it into food. Physicists will be able to probe what goes on inside the fiery heart of a star. Biologists can detect the very first stages of cancer and tailor new drugs to treat disease.

For several decades, scientists and engineers have been working with things measured in billionths of a meter (1 meter equals 39 inches) or moving at speeds measured in billionths of a second. This is called nanotechnology, from the Greek word "nanos," meaning dwarf.

Now they're venturing far deeper into this miniature world. They're timing events a million or billion times faster than a nanosecond and starting to measure things a trillion times smaller than a nanometer.

At that speed, "virtually all types of electronic motion, including those taking place deep in the interior of heavy atoms, could be frozen and visualized in slow-motion replay from a series of snapshots," said Ferenc Krausz, a pioneer in ultra-fast research at the Max-Planck-Institute of Quantum Optics in Garching, Germany.

This would help scientists "gain deep insight into the electrons' unexplored world and make them work for us in an optimum way," Krausz said in an e-mail message. "Researchers will be able to find out how electrons team up to form chemical bonds between neighboring atoms and how the creating or breakage of these bonds can be precisely controlled by light forces to form new molecules."

Researchers from the ultra-fast world discussed their latest findings earlier this month at a conference on "Attosecond Science" in Cambridge, Mass.

An attosecond is an almost inconceivably brief time: one billionth of a billionth of a second. For comparison, if an attosecond were stretched to the length of a full second, a second would last longer than 31 million years.

Attoscience is "truly on the forefront of science today," said David Reitze, a physicist at the University of Florida in Gainesville who attended the Cambridge conference.

"The ability to measure physical processes on attosecond time scales allows us to observe an electron move from one state to another state in an atom, molecule or solid," Reitze said.

"This is the first step to being able to control how electrons make these jumps, allowing us to dictate the course of chemical reactions," he said. "You can see why a pharmaceutical company might be interested in this."

The attosecond speed barrier was breached in 2001, when Krausz's team produced flashes of laser light lasting 650 attoseconds. Later that year, a French group got down to 250 attoseconds. In 2003 the group reached 130 attoseconds.

In March of this year, an all-European team led by Krausz reported that it can control electronic motion with a precision of 44 attoseconds. That's not much longer than it takes an electron to zip around the nucleus of a hydrogen atom.

"A pulse duration of well below 10 attoseconds should be feasible," Krausz said.

Other researchers are beginning to work with objects so tiny they're measured in "zeptograms," a thousand times smaller than an attogram.

For comparison, there are 28 grams in an ounce, and a zeptogram is a trillionth of a billionth of a gram. Three atoms of plutonium would weigh 1 zeptogram.

Physicist Michael Roukes and his colleagues at the California Institute of Technology have fashioned a miniature scale that measures weights to the nearest zeptogram. They used it to detect a cluster of 30 atoms of xenon, a rare gas in the atmosphere. The cluster weighed only 7 zeptograms.

"We anticipate this will offer an unprecedented opportunity for many interesting applications in surface science, atomic physics and biology," Roukes said at the March meeting of the American Physical Society in Los Angeles.

For more information on the Web, go to the American Institute of Physics' site at www.aip.org/pnu/2001/split/567-1.html

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The following are the scientific names for short intervals of time. The first column gives the name of the unit, the second column lists its equivalent to a second and the third column gives the unit's decimal version.

Unit Equivalent Decimal version

Second not applicable 1

Millisecond 1,000th of a second 0.001

Microsecond 1 millionth of a second 0.000001

Nanosecond 1 billionth of a second 0.000000001

Picosecond 1 trillionth of a second 0.000000000001

Femtosecond 1 quadrillionth of a second 0.000000000000001

Attosecond 1 quintillionth of a second 0.000000000000000001

Zeptosecond 1 sextillionth of a second 0.000000000000000000001

Yoctosecond 1 septillionth of a second 0.000000000000000000000001

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(c) 2005, Knight Ridder/Tribune Information Services.

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