NOBEL PRIZE in Physics...
Luis Frigo
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Date: Wed, 12 Oct 94 12:43:30 EDT
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Subject: update.198
PHYSICS NEWS UPDATE
A digest of physics news items by Phillip F. Schewe, American
Institute of Physics
Number 198 October 12, 1994 phys...@aip.org
THE 1994 PHYSICS NOBEL PRIZE goes to Bertram N.
Brockhouse of McMaster University in Ontario, Canada and to
Clifford G. Shull of MIT for their pioneering work in neutron
scattering experiments during the 1940s and 1950s. Quantum
mechanics holds that at the atomic level matter has both particle and
wavelike properties. Slow-moving neutrons, considered as waves, are
particularly valuable as a means of studying the structure and energy
properties of crystals. Partly this is because the equivalent
wavelength of the neutrons can be adjusted to match the spacing
between the atoms in the crystal, or because the energies of the
neutrons can be selected to match those of the characteristic vibrations
of the crystal. Shull is being recognized for his work on experiments
in which neutron waves fall on the crystal and scatter elastically (they
lose no energy) in a process called diffraction. By detecting the
scattered neutrons, the positions of the atoms in lattice can be
deduced. The neutrons can also scatter inelastically; that is, the
neutrons lose energy by creating modes of vibration (phonons) in the
crystal. In this case an analysis of the energies of the scattered
neutrons provides information about the energy states of the crystal.
Brockhouse won his half of the award for spectroscopic work of this
type. Neutron diffraction has an important advantage over x-ray
diffraction in that neutrons interact with (and therefore probe) the
crystal's magnetic structure, while x rays cannot. To this day, the
use of neutrons at many labs around the world (where, for example,
neutrons can be produced at fission reactors) is an important way of
studying diverse materials, such as biological samples and high-
temperature superconductors. Contact Brockhouse at 416-648-6329;
Shull at 617-862-8627. Magazine references: Scientific American,
June 1979 (an article on cold neutrons) and Physics Today, January
1985 (a special issue on neutrons.)
PERHAPS THE MOST CHEMICALLY ACTIVE FORM OF
MATTER IN NATURE are the bare uranium (U92+) ions recently
made by scientists at Lawrence Livermore National Laboratory (see
Update #185). The electrical attraction between such a heavy ion and
electrons on surfaces is immense. The Livermore researchers
(contact Ross Marrs, 510-422-3890) invented a tabletop device known
as the electron beam ion trap (EBIT) to make U92+ and many other
highly charged ions such as Xe44+. Although EBIT was originally
developed for trapping heavy ions, its mode of operation can be
modified to provide an efficient source of very slow, very highly
charged ions for collisions with surfaces. For instance, single-ion
impacts on insulators have led to the creation of nm-sized blister-like
defects. The volume of the defects can be controlled by varying the
charge of the incident ion. These properties may eventually lead to
applications in nanotechnology such as extremely high-density data
storage, nanoscale electronic circuit patterns, and micromachining.
(Physics Today, October 1994.)
ELEMENTS HEAVIER THAN ZINC have been detected in an
interstellar gas for the first time. Astronomers used the Hubble Space
Telescope to observe such elements as lead, arsenic, and krypton in
a gas cloud 400 light years away, a feat made difficult by the tiny
trace amounts of the elements in comparison to lighter elements.
(Sky & Telescope, Nov.)
CORRECTION. The Indian physicists who have sought evidence for
quark-gluon plasma (Update 197) work at the Cyclotron Centre in
Calcutta, not Bombay.
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Luis Antonio Frigo \ | / ~~~High LET Cosmic Rays~~~
lu...@physics.usfca.edu \ | / Physics Research Laboratory
laf...@lynx.cs.usfca.edu \|/ University of San Francisco
Work Phone 510-666-2333 * Golden Gate Ave. Cal U.S.A.
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