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Steven Chu, who won the 1997 Nobel Prize in physics for developing methods
to cool and trap atoms with laser light, will speak March 22 at
Carolina.
His free, public lecture, "Holding onto Atoms and Molecules with Laser
Beams," will be held at 7 p.m. in Hill Hall auditorium.
Chu is the third speaker in the Chancellor's Science Seminar Series, which
brings world-renowned investigators in the basic and applied sciences to
Carolina for lectures aimed at enhancing the public's awareness of scientific
discoveries and contributions to society. The series also highlights and
nurtures outstanding research at Carolina, said Greg Forest, series organizer
and senior associate dean in the College of Arts and Sciences.
"We at Carolina are enthusiastic about providing a steady stream of the
world's outstanding scientists for the public to enjoy and learn from," Forest
said. "Steven Chu surely fits this description. We hope a broad range of people
interested in this fascinating field will join us March 22nd. It's a unique
opportunity to hear and see one of the true great scientists of our time in a
forum for the general public."
Chu -- professor of physics and applied physics as well as the Theodore
and Frances Geballe professor in the School of Humanities and Sciences at
Stanford University -- has made major contributions in laser spectroscopy,
atomic physics, biophysics, polymer physics and quantum physics.
He pioneered work in the manipulation, cooling and trapping of neutral
particles by laser light. Techniques he created for laser cooling and trapping
atoms and other microscopic objects are being applied in wide-ranging areas of
physics, chemistry, biology and material science.
In 1997, the Nobel Prize committee honored Chu and two other investigators
for their ground-breaking work with atoms and lasers. Co-recipients were Claude
Cohen-Tannoudji, a professor at the College de France and Ecole Normale
Superieure in Paris, and William D. Phillips of the National Institute of
Standards and Technology in Gaithersburg, Md.
The idea of cooling atoms with laser light bucked conventional wisdom that
held shining light on something heats it up and, in the case of atoms, would
intensify their activity.
In 1985, however, Chu and colleagues at AT&T Bell Laboratories
discovered how lasers could form what Chu called "optical molasses," a
condition in which the intense concentrated light slowed the motion of select
atoms -- much like how the descent of a marble slows when it plops into a jar
of real molasses.
They also developed the first atomic trap that held the chilled atoms
still, permitting formation of a special liquid state possible only with
neutral particles at very low energy levels.
By slowing atoms down from typical speeds of 4,000 kilometers per hour to
speeds of less than a tenth of a kilometer per hour, optical molasses made
these atoms easier to study. Instead of rapidly disappearing, atoms caught in
optical molasses form what looks like a glowing cloud the size of a pea.
Previously, scientists could control the speed of electrically charged atoms by
using electrical and magnetic fields.
The Nobel Prize committee said Chu's technique advanced knowledge about
the interaction between light and matter. Scientists better understood gases at
low temperatures. That work allowed others to create a new state of matter
first discussed by Albert Einstein. Called a Bose-Einstein condensate, this
state involves atoms chilled to such a low temperature that their motion nearly
stops and the entire liquid droplet begins acting like a single entity, or
super atom.
Such research has implications for designing more precise atomic clocks
for use in space navigation, atomic interferometers to provide precise
measurements of gravitational forces, and atomic lasers, which could lead to
production of extremely small electronic components.
At Stanford, Chu has focused on applying and extending such techniques in
new areas. He and students built an atomic fountain. Laser-cooled atoms are
sprayed upward from an atomic trap like a jet of water. At the top of the
trajectory, the atoms are almost motionless for a moment. Then microwaves
beamed at them provide information about the atoms' inner structure. This work
could help develop a more precise atomic clock than exists today.
Chu's laboratory also is credited with inventing optical tweezers to study
the physical characteristics of individual polymer molecules. Some describe the
device as a microscopic version of a Star Trek tractor beam. Scientists can use
laser light to grip and manipulate a number of different kinds of microscopic
objects immersed in water.
In two 1997 papers, Chu and his students showed that studying polymers one
at a time can provide new insights into how the properties of polymeric
materials, such as plastics and synthetic and biological fibers, form from the
collective actions of individual molecules. In one study, they found that
individual polymer molecules appear to express an unexpected degree of
individuality. When forced to unravel in a strong current, apparently identical
molecules unwind in individual and unpredictable ways.
Chu and colleagues found that a single strand of polymer immersed in water
obeys the same simple law of motion as a plucked guitar string. Chu was
interested in the precision of the molecule's adherence to this law. Scientists
had believed such molecules would exhibit more complex behavior.
"We decided to take the analogy to the guitar string very seriously and
see how well it held up. It turned out to be much closer than we expected," Chu
has said.
A University of Rochester graduate, Chu earned a doctorate in 1976 at the
University of California at Berkeley, where he was a postdoctoral fellow. He
spent nine years at AT&T before joining Stanford in 1987.
A member of the National Academy of Sciences and the Academy of Art and
Sciences, Chu shared the King Faisal International Prize given by the Saudi
Arabian government in 1993 and received a Guggenheim Fellowship award in 1996.
A year earlier, Chu won the Science for Art Prize given by LVMH Moet Hennessy
Louis Vuitton Inc. for an entry based on his research. He is a fellow of the
American Physical Society and the Optical Society of America, which honored him
for achievements in laser science and spectroscopy, respectively.
Besides the lecture, Chu will participate with public school students in a
teleconference run by LEARN North Carolina (Learners' and Educators' Assistance
and Resource Network), part of the School of Education.
Pierre de Gennes, the 1991 Nobel laureate in physics, kicked off the
Chancellor's Science Seminar Series in 1999. Last November, Mario J. Molina,
the 1995 Nobel Prize winner in chemistry, spoke in Memorial Hall. For more
information, see http://www.unc.edu/css/
Other campus lectures by Chu
Besides his public lecture, Steven Chu will give the annual Rohm and Haas
Lectureship in materials chemistry hosted by the Curriculum in Applied and
Materials Sciences.
Anyone interested in the sciences is encouraged to attend the free
lectures, which are:
* "Looking at Polymers in Shear and Elongational Flows, One Molecule at a
Time," March 22 at 3 p.m. in 207 Venable Hall; and * "Watching Individual Enzymes Work, Unfold and Refold in Real Time,"
March 23at 2:30 p.m. in 207 Venable Hall.
The lectureship is sponsored by the Rohm and Hass Co. As part of the
event, Chu will meet with faculty, students and others affiliated with the
applied and materials sciences curriculum and several related
departments.
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