FOR BENEFITS OF MATTER-STRUCTURE RESEARCH, CHECK AT HOME
Author: By David Chandler, Globe Staff
Date: Thursday, October 13, 1994
Page: 25
Section: NATIONAL/FOREIGN
For a hint of the breadth of discoveries that flowed from the work that
earned the Nobel Prize in physics yesterday, just look at your refrigerator
door.
The lightweight magnets that helped turn refrigerators into bulletin boards
in millions of households were but one of many indirect offshoots of the
prize-winning research.
The award recognized the impact of the technique known as neutron
scattering, one of the most useful methods scientists have for looking deep
within a solid piece of matter to see how its atoms are arranged.
Many of the most important advances in materials science in the last few
decades -- high-temperature superconductors, plastic polymers, new magnetic
materials and amorphous semiconductors used in solar cells -- have been based
on, or explained by, research using neutron scattering, which Clifford Shull
and Bertram Brockhouse developed more than 40 years ago.
The technique, which can reveal exactly how atoms are arranged inside a
sample of matter, has had "an influence on virtually every area of condensed
matter physics" -- the study of the basic properties of solids and liquids --
said Thomas Greytak, a professor of physics at the Massachusetts Institute of
Technology. "It's a technique that's used universally."
Not only did the pioneering development affect most work in the field
since, Greytak said, but "they had so much insight that the experiments they
did in the first five years basically laid the groundwork for all the work
since."
Starting in the late 1940s, MIT Dean of Science Robert Birgeneau said, the
two scientists "realized that you could use beams of neutrons to investigate
the structure of matter. Shull developed the technique to look at the static
structure, while Brockhouse showed how to look at the dynamic structure."
Or, as the Nobel citation put it, Shull "has helped to answer the question
of where atoms 'are,' " and Brockhouse "the question of what atoms 'do.' "
The technique involves directing a beam of particles produced by a nuclear
reactor at a sample of the material to be studied. Like a stream of pellets
striking an object, the subatomic particles bounce off in various directions
depending on the target's shape and structure. By analyzing the scattering
pattern, scientists can produce a detailed picture of the arrangement of atoms
in the sample.
Birgeneau said one reason the method is so useful is that "neutron beams
are very penetrating. Unlike X-rays, which only probe the first 1/1000 of an
inch" of a solid, "neutron beams can probe an inch deep."
In the currently intense research into high-temperature superconductors --
materials that lose all resistance to electricity -- almost all the analysis
of the structure of these complex ceramic compounds has been done by neutron
scattering. The findings are helping to develop better superconductors, which
may someday improve the efficiency of long-distance power wires, enable the
massive storage of electricity during off-peak hours and lead to new
transportation systems such as magnetic levitation trains.
It also is used to study the magnetic properties of metals, including how a
metal becomes magnetized. That helped in developing new magnetic materials
used in everything from computer memories and audio and video recorder heads
to the lightweight version of the ubiquitous refrigerator magnets.
The method has also played a key role in biology, because it allows
scientists to see the placement of hydrogen atoms in a material, Birgeneau
said.
The Nobel recognition, he said, was overdue: "We've been waiting for years
for this to happen."
CHANDL;10/12 NIGRO ;10/13,10:29 MATTER13
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