Number 245, October 18, 1995 by Phillip F. Schewe and Ben Stein
THE 1996 NOBEL PRIZE FOR CHEMISTRY goes to Mario Molina of MIT, T. Sherwood
Rowland of UC Irvine, and Paul Crutzen of the Max Planck Institute in Mainz,
Germany for their work on the ozone depletion problem. Ozone molecules
high in the stratosphere help protect living organisms from the hazardous
effects of solar ultraviolet radiation. Unfortunately, in recent decades
the maintenance of ozone in the atmosphere has been partially disrupted
by a complex series of chemical reactions arising from anthropogenic compounds,
especially chlorofluorocarbons (CFCs), which are used as refrigerants.
The seasonal lowering of ozone densities is particularly prominent over
Antarctica. In a way this year's chemistry prize is the first Nobel to
recognize environmental research. Crutzen did early work (1970) on the
role of nitrogen oxides in reducing ozone. Molina's and Rowland's research
showed that CFCs were not as inert as had been thought and that they posed
a threat to ozone. Their work, conducted in the face of great skepticism
by some scientists and at a time before the famous Antarctic "ozone
hole" had been discovered (1985), led to the establishment of restrictions
on CFC usage.
ATOMS HAVE BEEN GUIDED THROUGH HOLLOW OPTICAL FIBERS , introducing a
potentially convenient and flexible method for manipulating atoms and perhaps
measuring their wavelike properties. Taking a hollow glass fiber and filling
it with laser light, a Colorado group (including Dana Anderson and Eric
Cornell, 303-492-6281) has steered rubidium atoms through the twists and
turns of fibers with cores as narrow as 10 microns. By making the laser
light brightest at the center of the core, and tuning the laser just below
the frequency at which the atoms absorb the maximum amount of light, the
researchers ensure that the atoms are attracted to the core's center region
as they travel through the fiber. This technique will be useful for moving
atoms from a high-density source into an ultra-high vacuum environment
in atom physics experiments. It might be possible to make atom-scale electronic
circuits by performing "lithography in reverse": instead of using
chemicals to etch away features on a silicon wafer, one would use the fiber
as an "atomic fountain pen" to spray atoms onto the surface.
There is also the possibility of performing "fiber-atom interferometry."
If the atoms are cold enough and the fiber narrow enough so that the atom's
wavelength is comparable to the diameter of the fiber, it will act as an
atom wave. By splitting the fiber in two, the atom would split into a pair
of wavelets which could be later recombined to produce an interference
pattern. (M.J. Renn et al, 30 October 1995, Phys. Rev. Lett.; journalists
can obtain text and figures from AIP Public Information, physnews@aip.org)
SUBSURFACE ISLANDS---A NEW GROWTH MODE . Lead and copper are normally
immiscible in bulk; one would expect that adding copper atoms to a lead
substrate would result in the buildup of copper islands at the surface.
But now scientists at the Technical University of Vienna in Austria and
the University of Osnabruck in Germany have observed (with a scanning tunneling
microscope) the growth of tiny three-dimensional copper islands (3-11 layers
thick) in the body of a lead substrate. The Cu chunks are paved over with
a single layer of Pb atoms. (C. Nagl et al., Physical Review Letters, 16
October 1995.)
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