Professor Emeritus Clifford G. Shull has won the 1994 Nobel Prize in physics for pioneering work he did almost 50 years ago on neutron diffraction, a technique that probes how atoms in a material are arranged.
He is the fourth MIT professor to win a Nobel Prize since 1990.
Professor Shull shares the prize of about $930,000 with Professor Bertram N. Brockhouse of McMaster University in Canada. Professor Brockhouse developed the technique of neutron spectroscopy, which allows scientists to explore atoms' movements within a material.
"In simple terms, Clifford G. Shull has helped answer the question of where atoms `are' and Bertram N. Brockhouse the question of what atoms `do'," the Royal Swedish Academy of Sciences said in announcing the prize.
"Most people know that X-ray methods and microscopy can be used for studying objects in detail. [But] despite refinements these methods are not always adequate. The researchers now rewarded have developed neutron scattering techniques, powerful methods of analyzing both solid and fluid matter."
Understanding where atoms are in a material and how they interact with one another is key to understanding a material's properties. "Then having understood these properties, we can think of how we can improve on things," said Professor Shull, 79, at a press conference October 12, the day of the Nobel announcement. "How can we make better window glass, better semiconductors, better microphones? All of these things go back to understanding the basic science behind their operation."
The Nobel citation noted that thousands of people now work in the field of neutron scattering, using the technology to study ceramic superconductors, the structure of viruses, surfaces of relevance to catalytic exhaust cleaning, and more.
EARLY MORNING CALL
Professor Shull said he "stumbled out of bed" to answer a phone call at around 5:30 in the morning last Wednesday. The caller, a member of the Nobel committee, told him he had won the prize.
Asked whether he'd expected a Nobel for his work, Professor Shull replied: "A prize like this is something nobody seriously thinks about in connection with his own background. I'm surprised."
But his wife Martha told the Boston Herald that she thought the honor was long overdue: "People kept winning [the prize] based on the work he did so I just figured they ought to have given it to him one of those years."
Sitting at the press conference table with Professor Shull were Martha-"my compatriot," he said-Provost Mark S. Wrighton, Dean of Science Robert J. Birgeneau, and Professor Ernest J. Moniz, head of the Department of Physics.
A beaming Dean Birgeneau said of Professors Shull and Brockhouse: "Both Cliff and Bert are renowned in the community, first of all obviously as great scientists, secondly as great teachers (they've produced a generation of people after them who are now the leaders of the field), and thirdly both as really fine, warm human beings who have been wonderful academic colleagues.
"So I can't tell you how much pleasure it gives us that these two wonderful people have been recognized by the Nobel Prize committee this year."
Dean Birgeneau, a former head of the physics department, is also a researcher in solid-state physics. "I've followed in [Cliff and Bert's] footsteps," he said. Later he noted for Tech Talk that "the very first data I ever analyzed was in [Professor] Brockhouse's group at Chalk River Labs."
TOWARD USEFUL NEUTRONS
Professor Shull began his award-winning work in 1946 at what is now Oak Ridge National Laboratory. At that time, he said, "scientists at Oak Ridge were very anxious to find real honest-to-goodness scientific uses for the information and technology that had been developed during the war at Oak Ridge and at other places associated with the wartime Manhattan Project."
Professor Shull teamed up with the late Ernest Wollan, and for the next nine years they explored ways of using the neutrons produced by nuclear reactors to probe the atomic structure of materials.
When a beam of neutrons is directed at a given material, they "bounce against (are scattered by) atoms in the sample being investigated [and] their directions change, depending on the atoms' relative positions," the Nobel citation said. "By counting the neutrons in a rotatable detector, a diffraction pattern" of those positions can be obtained. "It is for this variant of the neutron scattering technique that [Professor] Shull has been awarded his Nobel Prize."
Professor Shull told the New York Times: "I only wish that Dr. Wollan were still alive to share in this prize."
BASIC CONTRIBUTIONS
Professor Shull went on to use this neutron-scattering technique to make many basic contributions to science. For example, his "studies of simple crystals laid a basis for the interpretation of the very complicated structures being analyzed by modern neutron crystallographers," the Nobel citation said.
In Professor Shull's opinion the most important problem he worked on at the time dealt with determining the positions of hydrogen atoms in materials. "Hydrogen atoms are ubiquitous in all biological materials and in many other inorganic materials," he said, "but you couldn't see them with [other techniques like X-ray diffraction].
"With neutrons it turned out that that was completely different, and we were very pleased and happy to find that we could learn things about hydrogen-containing structures."
Through these initial experiments "Shull opened what was to become a very large field for finding out how hydrogen is bound in, for example, ice, metallic hydrides and organic compounds," the Nobel citation said.
Dean Birgeneau noted that Professor Shull also initiated the "first neutron diffraction investigations of magnetic materials, thence yielding for the first time information [about] the magnetic properties of materials at the atomic level." These experiments opened up an entirely new field of study.
And if that weren't enough, Professor Moniz noted that "Cliff also studied the fundamental properties of the neutron itself."
For all of this and more, "if there is a `Central Clearing House for Thermal Neutron Physics,' or a `Father of Neutron Scattering' in the United States, it is Shull," wrote Professor Anthony Nunes of the University of Rhode Island in a biographical sketch of Professor Shull, who was Nunes' thesis advisor at MIT. Professor Nunes, MIT PhD 1969, wrote the piece for a 1986 Physica.
MODEST TO A FAULT
Professor Nunes went on to note that Professor Shull's "abilities as an experimental physicist are amplified and extended by his completely candid relations with coworkers" who "find him to be modest to a fault. He is very careful to `give credit where credit is due,' usually citing originators of ideas even in casual conversation."
He concluded: "If there is any complaint to be lodged by a former student [of Shull's], in my opinion it would be this: With his easy-going competence and professional [demeanor] he might be said to have insulated us from the administrative details of proposal writing, report deadlines and the sometimes violent professional jealousies of the real world.
"Nonetheless, I consider the intellectual stimulation, the unending optimism and the simple scientific fun of my student years with this man to be priceless."
Professor Shull is the fourth member of the MIT physics faculty to receive the Nobel Prize in physics and the 15th present or former faculty member to receive a Nobel Prize. One staff member and 11 alumni also have won Nobels.
Professor Shull came to MIT as a full professor in 1955 and retired in 1986, though he still visits to "look over the shoulders" of students doing experiments in the "remnants of my old research laboratory."
His awards include the Buckley Prize, which he received from the American Physical Society in 1956, and election to the American Academy of Arts and Sciences (1956) and to the National Academy of Sciences (1975). In 1993 he received the Royal Swedish Academy of Sciences' Gregori Aminoff prize for his "development and application of neutron diffraction methods for studies of atomic and magnetic structures of solids."
Born in Pittsburgh, PA, in 1915, Professor Shull graduated from Schenley High School in Pittsburgh then received his BS from Carnegie Institute of Technology (now Carnegie Mellon University) in 1937. He entered Carnegie Tech to study aeronautical engineering, but after six months found himself drawn to physics. He received the PhD from New York University in 1941.
He was a teaching assistant at NYU from 1937 to 1941, a research physicist with the Texas Company (now Texaco) in Beacon, NY, from 1941-46, and a research physicist at Oak Ridge National Laboratory from 1946-55.
Professor Shull and his wife of 53 years, Martha-Nuel Summer live in Lexington. They have three sons-John C., Robert D., and William F. Shull-and five grandchildren. One of their grandchildren, Craig M. Shull, is a junior in mechanical engineering at MIT.
A version of this article appeared in the October 19, 1994 issue of MIT Tech Talk (Volume 39, Number 8).
