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  October 21, 2002

Stwalley's Ultracold Research
Places Him at Frontier of Physics
By Claudia G. Chamberlain

Since high school, when he won a scientific encyclopedia and a slide rule in a mathematics competition, the world of discoveries has been William Stwalley's domain.

And from the early 1960s, when he was a student at the California Institute of Technology, to the end of that decade when he received a Ph.D. in physical chemistry from Harvard University, Stwalley's world of science has revolved around the complexity of atoms and molecules.

Image: Bill Stwalley
Board of Trustees Distinguished Professor Bill Stwalley conducts research on ultracold molecules and is an authority on the interaction of atoms over large distances.

Photo by Shannon McAvoy

Now a professor and head of the physics department at UConn, he studies atoms and molecules at ultracold temperatures, in collaboration with fellow physics professors Phillip Gould and Edward Eyler.

Ultracold temperatures are those as cold as one-millionth of room temperature.

"In some sense, going to lower and lower temperatures is a final frontier of physics," says Stwalley. "It's definitely a promising frontier."

Many areas of atomic, molecular, and optical physics have been significantly influenced by his work, and peers consider him the world's leading authority on the interaction of atoms over large distances.

Colleagues say no one has contributed more than Stwalley to the general understanding of alkali-metal diatomic molecules, which involve the putting together of two atoms to make a molecule, and the subsequent delving into the fundamental aspects of chemistry.

"In terms of applications, Bill has done a great deal of work on cold molecules, and physicists and chemists are always interested in understanding how chemical reactions or collisions between atoms and molecules take place," says Gould.

"With Bill's work on cold molecules, we're now able to explore these things in a new regime," Gould adds. "Basically, it's a factor of a billion degrees colder than room temperature. It's not just, 'let's cool it a few more degrees'. This is a big jump and, hopefully, we'll learn some new physics."

Stwalley arrived at Storrs in 1993 to serve as professor and head of the physics department and director of the University's laser facility, as well as affiliate professor of chemistry, titles he continues to hold today.

Gould and other colleagues say Stwalley has instilled a strong spirit of cooperation and collaboration among the physics faculty and has elevated the atmosphere of research. The collaboration now extends to a European scientific training and research network involving 11 other institutions.

Stwalley is also credited with introducing to the department in 1995 a National Science Foundation-funded program, Research Experience for Undergraduates, an annual summer program that not only benefits UConn physics majors, but also brings students from other universities to Storrs. He also assisted in the development of a photonics minor, which gives physics majors and students in the School of Engineering training in laser-based technologies.

Stwalley's interest in science was piqued in high school by a math teacher named Mr. Redfern. If Mr. Redfern had a first name, it's a discovery Stwalley missed. "In the old days, you just didn't know your teacher's first name," he says.

It was Redfern who took Stwalley and other students all over California to participate in math competitions. Most often, it was Stwalley who came home with the top prize.

With encouragement from his father, an aerospace worker at the then Douglas Aircraft Co., Stwalley was accepted at the California Institute of Technology, where he became involved in research analyzing data and experimenting with the colors of sunlight. The experience put him on a path to quantitative research.

Encouraged by his West Coast professors to go East, Stwalley headed to Harvard University and immersed himself in the interaction between atoms and molecular beams.

At Harvard, he was introduced to spectroscopy, or the probing of light admitted to a system and that led to his expertise today as a leading molecular spectroscopist. He also met Dudley Herschbach, a science professor who became his mentor and friend.

"It was pretty clear that Bill was going to do well," recalls Herschbach, 70, who has taught at Harvard for nearly 40 years. "Bill was outstanding and has contributed to science in a meaningful way."

Later, during a teaching and research career at the University of Iowa that spanned a quarter of a century, Stwalley is credited with proposing that the phenomenon of Bose-Einstein condensation could be achieved in a gas of spin-polarized hydrogen. A Bose-Einstein condensate is a form of matter into which atoms can coalesce at ultracold temperatures. Stwalley's proposal created tremendous excitement within the physics community.

"Bill's early contribution with Bose-Einstein Condensation recognized the potential of an atomic system, and his original idea got others thinking," says Gould.

Currently, a team of UConn professors including Stwalley are hoping to establish a Quantum Information Research Institute. The Institute would address the problems of fundamental quantum information and quantum computing, as well as applications such as secure communications, code breaking, and large-scale information processing.

Says Stwalley: "Quantum information is a hot topic. A code that would take the age of the Universe for the present computers to break could conceivably be broken on a quantum computer in mere minutes. Ultracold atoms and molecules are promising as possible 'qubits' of a quantum computer."

Earlier this year, Stwalley was named a Board of Trustees Distinguished Professor, the highest academic title a UConn professor can attain. He has received a variety of other significant awards, including the 1998 William F. Meggers Award from the Optical Society of America for outstanding work in spectroscopy.

But for Stwalley, some of the most important rewards come literally in all shapes, sizes, and nationalities:

"It's exciting," he says, "to be in the research lab with my students."

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