Ahmed Zewail is director of the Center for Ultrafast Science & Technology at Caltech and one of three US Science Envoys to the Middle East. His precision array of lasers, mirrors, prisms, molecular beams and detection equipment in the lab known as “Femtoland” constitutes the world’s fastest imaging technology—the world’s fastest “camera.”

arm, late-afternoon sunlight streams through the window of a small room in the town of Desuq, in Egypt. The year is 1960, and a teenager studiously attacks a long list of math and chemistry problems. While he works, the voice of renowned Egyptian virtuoso Umm Kulthum filters from his family’s radio. When one song ends, he turns the dial, searching station after station to catch another of her hour-long songs of longing, loss and love. He’s good at cracking the math problems, and—rather than distracting him—Umm Kulthum’s music makes long hours of study a joy and a pleasure.

The boy’s parents have high hopes for his future. They’ve hung a sign on his door that says “Dr. Ahmed.” And Ahmed Hassan Zewail will grow up to more than fulfill his family’s hopes and expectations: In 1999, as a professor at the California Institute of Technology (Caltech), he will be awarded the Nobel Prize for Chemistry, becoming the first Egyptian—and the first Arab—to win a Nobel in a scientific field. And in 2009, his career will come full circle when he is named one of the first three “scientist-diplomats” in the United States’ new Science Envoy program, aimed at forging scientific and technological partnerships in the Muslim world to help meet global challenges in health, energy, the environment and water and resource management.

The love of science and math and the love of Egyptian culture are interwoven throughout Zewail’s life history. His 1946 birthplace was Damanhur, which, as he enjoys pointing out, lies between Alexandria and Rosetta, two cities noted for their importance to the world’s intellectual heritage. The famous Rosetta Stone, which Jean-François Champollion used to decode ancient Egyptian hieroglyphic and demotic texts, was unearthed in Rosetta in 1799. And the renowned Library of Alexandria was the greatest library of ancient times, containing hundreds of thousands of papyrus scrolls. For Zewail these cities were more than aspects of local history; they were an inspiration to scholarship.

His growing-up in Desuq, a small town on the east bank of the Rosetta branch of the Nile, was a magical time for Zewail. He writes lovingly of his mother, Rawhia Dar, and father, Hassan Ahmed Zewail. His parents strongly supported his study of science and only lightly chastised him when he missed a point or two on a test at school. But in many ways, he notes in his autobiography, “we had a much bigger family—the people of Desuq. Families knew each other well, shared happy and difficult times, and valued interdependence….” At dawn, Zewail and the other children of Desuq rose and went to study at the nearby Sidi Ibrahim al-Desuqi mosque—a place of learning as well as prayer.

Fascinated by how science and technology worked, Zewail, then a student, once used an Arab coffee-roaster to heat wood chips in a test tube in an attempt to produce wood gas. To test whether his experiment was succeeding, he applied a lit match to the output of his apparatus and nearly set his bedroom aflame. On another occasion, the young Zewail decided to take his uncle’s car out for a spin. He’d never had a driving lesson, but he’d learned how a car operated—in theory. His drive along the banks of the Nile barely avoided a potentially fatal plunge into the river. Decades later, in 1999, when he was awarded Egypt’s highest state honor, he remembered his days growing up along the Nile. Egypt has never been far from his thoughts.

Zewail studied chemistry at the University of Alexandria and upon graduation in 1967 was appointed as a moeid, or demonstrator, at the university, teaching undergraduates while conducting his own graduate studies. One of the biggest decisions he made at this time was to leave Egypt in 1969 and go to America to pursue a Ph.D. at the University of Pennsylvania.

America presented Zewail with cultural and language challenges, but did not dim his vibrant optimism. Earning his Ph.D. in chemistry in 1974, he moved west to the University of California at Berkeley and then, in 1976, joined the faculty at Caltech, arriving with a raft of published scholarly papers in chemistry and physics to his credit.

At Caltech, Zewail proposed investigating what physicists and chemists call coherence; he contemplated experiments to study this phenomenon in single molecules as well as among billions of them. The difference between coherent and incoherent molecular vibration is akin to the difference between a marching band and a random crowd of people walking down the sidewalk: The feet of people in a crowd move in a random, incoherent manner; a marching band displays coherence when each musician moves his or her feet up and down in unison, in step with the music. If you know someone is in the marching band, then you can tell how that person’s feet are moving by watching the whole band—you don’t have to pick out the individual. Similarly, on the atomic level, you can study the vibrations of a molecule if it is part of a large group of coherently vibrating molecules. And if you know how molecules vibrate, you can begin to predict how they will react with each other—which is the essence of the science of chemistry.

COURTESY NOBEL FOUNDATION / CALTECH

Zewail’s “camera” does not use film: It captures a spectroscopic image that indicates molecular masses at the moment of “exposure”—the “observation pulse.” Varying the time lag between the start pulse and the observation pulse is accomplished by moving mirrors by a few microns (thousandths of a millimeter) to create the time-sequence imagery that shows the stages of chemical reactions over femtosecond spans of time.

A femtosecond is an excruciatingly short period of time. One femtosecond is one millionth of one billionth of a second. That fraction is written 10^-15 in scientific notation, and the word comes from the Swedish word femton, “fifteen.” One femtosecond is as much smaller than one second as the thickness of a human hair is smaller than the distance to the Moon. If you moved at the speed of light for one femtosecond, you’d only travel 30 micrometers, or about 0.0012 inches: Femtoseconds are so short that light couldn’t get even a third of the way across a human hair in one femtosecond.

The fastest chemical reactions—such as the twisting of a molecule of retinal in your eye that allows you to perceive light—take about 200 femtoseconds to occur. To observe molecular transformations at high definition requires two laser pulses about 10 femtoseconds apart—and adjusting that time gap by making tiny changes in the positions of the mirrors shown in the diagram above allows scientists to visualize every stage of the transformation.

Some of his chemistry colleagues argued that Zewail’s experiments with coherence would never succeed. But he pushed ahead to do experiments that others thought theoretically impossible, perhaps because his youthful experience crashing his uncle’s car had taught him the difference between theory and practice. Zewail’s belief in coherence was justified in 1980 when he and his fellow researchers demonstrated coherent vibrations in isolated molecules of the hydrocarbon anthracene. This demonstrated the reality of coherence within molecules and put chemists on the road to using coherence to predict chemical behavior; it was his first major breakthrough.

Zewail wanted to see further. Although he’d never used a laser before coming to America, Zewail recognized that if you had a laser that produced very short pulses of light, you could use it to watch chemical reactions actually happening. To work, though, the pulses had to be extremely short—only a few femtoseconds in duration, a billion times shorter than had been achieved until then. At Bell Labs, Erich Ippen and Charles Shank developed the first femtosecond laser and Zewail integrated it into his apparatus.

Chemical bonds are the glue that holds atoms together—whether the atoms make up a crystal, a leaf or your hand. If we could see bonds forming or bonds breaking, we’d have a much better understanding of how chemical reactions occur. Chemists know, for example, that when they burn charcoal, oxygen atoms bond with carbon atoms to form carbon dioxide (CO₂). They know what the starting materials are and what the end product is, but actually watching the reaction occur was impossible—before Zewail.

DIAGRAM: COURTESY NOBEL FOUNDATION / CALTECH

Molecules, like everything in nature, seek the lowest possible energy state. The cyclobutane molecule, above, top left, comprises four bonded carbon atoms. (Each carries two hydrogen atoms.) Zewail’s Nobel Prize-winning breakthrough showed that when excited by a laser pulse for a few femtoseconds, the molecule goes through a two-stage transition, center, in which two of the four carbon atoms break apart, while the other two remain bonded. From this transition state, which lasts a few hundred femtoseconds, the reaction’s second step goes one of two ways: Either the second carbon bond breaks, producing two ethylene molecules, right, or the first carbon bond re-forms, which drops the molecule to its lowest energy state, lower left. By showing the properties of the transition state—by opening chemical transition states to observation and thus prediction and perhaps manipulation—Zewail created “femtochemistry.”

To study chemical bonds, you need to be fast. Bonds break and form so very quickly that you need an extremely fast “camera” to take stop-action pictures of two atoms approaching each other and forming a chemical bond. This is what Zewail figured out how to do: use a laser “camera” fast enough to take stop-action “pictures” of atoms as they formed or broke bonds. Zewail needed to set up a very precise molecular beam: a stream of molecules shooting out of a small nozzle at supersonic speeds. Different stages of chemical reactions that occur within the molecular beam will be found at different distances from the nozzle as the molecules jet away. The high speed of the molecular beam serves to spread the reaction out in space. Reactions in progress can then be “photographed” using a femtosecond laser aimed across the path of the beam, as in the diagram at the top.

To do this, Zewail needed a laser capable of emitting ultra-short femtosecond pulses of laser light. Zewail’s research group at Caltech was among the first to acquire such a laser, and he and colleague Dick Bernstein coined the word “femtochemistry” to describe the field of chemistry that studies the making and breaking of chemical bonds. Scientists at Caltech and elsewhere have been using femtochemical techniques to study biological systems, such as how oxygen binds to hemoglobin in the blood or how retinal in the eye changes its shape to signal a protein called opsin to trigger excitation of the optical nerve and thus vision. Zewail predicts that femtochemical techniques may eventually allow us to do “laser-selective chemistry,” in which we use laser beams to manipulate bonds to create entirely new molecules.

The first chemical reaction that Zewail and his colleagues studied with the femtosecond laser apparatus was the breaking of a chemical bond. In late 1986, they aimed their femtosecond laser at the simple molecule iodine cyanide (ICN) and watched as the bond between the iodine atom and the carbon atom of the cyanide group stretched and then snapped. The bond broke “little by little, the first time such a thing had ever been witnessed in real time,” Zewail wrote. This was his second major scientific breakthrough.

The impact of Zewail’s research was acknowledged when he was awarded a solo Nobel Prize. The Swedish Academy of Sciences noted that Zewail “brought about a revolution in chemistry” by enabling us to “see the movements of individual atoms.” The Nobel Prize committee recognized that Zewail’s work allows us to “understand and predict important [chemical] reactions.” Today, Zewail is the Linus Pauling Professor of Chemistry, professor of physics and director of the National Science Foundation Laboratory for Molecular Sciences at Caltech. He is widely respected as the founder of the field of femtochemistry and continues to build on the work that won him the Nobel Prize. Currently, he and his colleagues are developing techniques for four-dimensional (that is, the familiar three dimensions of space plus time), ultra-fast electron microscopy and diffraction. Among many other applications, these techniques will be used to study the folding of proteins and their misfolding, which appears to be involved in a number of diseases such as Alzheimer’s and in some forms of obesity.

Seeing beyond the walls of his laboratory, Zewail frequently gives public lectures stressing the importance of fundamental scientific research. Although declining numbers of students choose to major in the sciences, he is optimistic that this decades-old trend can be reversed. With one foot in America and one in Egypt, he is perhaps uniquely situated to understand the difficulties faced by scientists in both countries. “I am an optimist,” he says, and at every opportunity he speaks about the importance of the promotion of science and technology in developing countries. “Young scientists,” he says, “shouldn’t have to leave Egypt to dream big and to engage in frontier science and technological advancements.” In Egypt, he has promoted the building of a new university of science and technology on the outskirts of Cairo. This new institution, he hopes, will grow to become Egypt’s own Caltech.

One of the remarkable aspects of Zewail’s autobiography, Voyage Through Time, is that it is replete with the names of hundreds of friends and acquaintances, ranging from Umm Ibrahim, the street vendor who sold him falafel sandwiches during his school days, to President Hosni Mubarak of Egypt. Over the years, he has worked with more than 300 scientists, graduate students, postdocs and other researchers—about 10 percent of them fellow Arabs—from around the globe. That collaboration will only grow with Zewail’s appointment as a Science Envoy, announced by Secretary of State Hillary Clinton in Morocco November 3, which followed his appointment earlier in 2009 to President Obama’s Council of Advisors on Science and Technology. The Caltech professor called the assignment as a scientist-diplomat “a great honor,” and added that, after years of researching the dynamics of chemical bonds, “I look forward to helping forge new bonds among nations.”

Ahmed Zewail now lives and works half a world away from his Egyptian birthplace. He is both Egyptian and American. But the heat of the Egyptian sun still warms his personality and his heart is still brightened by the music of Umm Kulthum. In his office at Caltech, he still listens to CD recordings of her voice as he works on a new set of problems in science—and in the world.

	Geochemist, mineralogist and science writer Andrew A. Sicree (sicree@verizon.net) teaches university geosciences and conducts research for mining, oil and gas industries. He lives and works near State College in central Pennsylvania.
	Nik Wheeler (www.nikwheeler.com) first worked for Aramco World and Saudi Aramco World in the 1970’s, illustrating some 20 articles as well as special issues on Central Asia, China and the Silk Roads. His most recent book, The Most Beautiful Villages and Towns of the Southwest, is published by Thames and Hudson. He lives in Santa Barbara, California.