Fun_People Archive
21 Feb
Bits o' Physics - update.471

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From: Peter Langston <psl>
Date: Mon, 21 Feb 100 13:28:19 -0800
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Subject: Bits o' Physics - update.471

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Excerpted-from: PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 471  February 17, 2000   by Phillip F. Schewe and Ben Stein

QUANTUM MIRAGE.  The scanning tunneling microscope (STM)
allows one both to push individual atoms around on a surface and to
image them.  Especially intriguing are images of "quantum corrals,"
circular or elliptical arrangements on a surface inside of which the waves
corresponding to electrons near the substrate surface can be revealed.  The
latest entry in the gallery of fine pictures comes from IBM, where
physicists placed 36 cobalt atoms in an elliptical "Stonehenge" pattern on
a copper surface.  An extra magnetic cobalt atom was placed at one of the
two foci of the ellipse, causing visible interactions with the surface
electron waves.  But the waves seem also to be interacting with a phantom
cobalt atom at the other focus, an atom that is not really there.
(Manoharan, Lutz, Eigler, Nature, 3 Feb 2000; see figure at
www.aip.org/physnews/graphics.)

ATTOSECOND LIGHT PULSES.  A curtailed wave pulse can be
represented mathematically as the weighted sum of a number of
wavetrains of various wavelengths.  In this way, scientists at the
Foundation for Research and Technology-Hellas (FORTH) in Crete have
created light pulses less than a femtosecond (10^-15 seconds) in duration
(Papadogiannis et al., Physical Review Letters, 22 November 1999).  First
they split a beam of light (wavelength of 800 nm ) into two parts; each of
these, when sent through an argon vapor, produces sets of higher-
harmonic wavetrains (at wavelengths equal to several fractions of the
original 800 nm) which add together in a synchronized way to form the
ultrashort wave pulse with a duration estimated to be less than 100
attoseconds.  Before this the record short pulse was 4.5 fs in duration.
(Physics World, Feb 2000.)

© 2000 Peter Langston