PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 648  July 31, 2003   by Phillip F. Schewe, Ben Stein, and
James Riordon

A WATER MOLECULE'S CHEMICAL FORMULA IS REALLY NOT H2O, at least from
the perspective of neutrons and electrons interacting with the
molecule for only attoseconds (less than 10^-15 seconds). According
to new and recent experiments, neutrons and electrons colliding with
water for just attoseconds will see a ratio of hydrogen to oxygen of
roughly 1.5 to 1, so a more accurate formula for water under these
circumstances would be H1.5O.  According to the experimenters (Aris
Chatzidimitriou-Dreismann, Technical University-Berlin,
dreismann{at}chem.TU-Berlin.de, 011-49-30-314-22692), this "opening of
the attosecond time window" may be revealing dramatic quantum
effects that were once too short-lived to catch.  Nonetheless, such
effects may revise conventional textbook notions of water and other
everyday molecules.  Moreover, these experiments can provide new
insights on chemical reactions at the 100-500 attosecond scale: the
neutron and electron probes break apart the chemical bonds in
molecules, as compared to laser-based attosecond studies, which have
just ejected electrons from atoms at this point.
The story begins in 1995. At the ISIS neutron spallation facility in
the UK, a German-British collaboration collided epithermal neutrons
(those with energies of up to a few hundred electron volts) with a
target that included water molecules (Chatzidimitriou-Dreismann et
al., Physical Review Letters, 13 October 1997). Detecting the number
and energy loss of the scattered neutrons in the resulting
attosecond-scale collisions, the researchers noticed that neutrons
were scattering from 25% fewer protons than expected.   Apparently,
the protons in hydrogen were sometimes "invisible" to the neutron
probes. While the exact details are still being debated by
theorists, the researchers' own theoretical considerations suggest
the presence of short-lived (sub-femtosecond) entanglement, in which
protons in adjacent hydrogen atoms (and possibly the surrounding
electrons) are all interlinked in such a way as to change the nature
of the scattering results. Realizing that water itself has anomalous
properties, the researchers repeated the neutron experiments in
other more typical molecules, for instance in benzene
(conventionally noted as C6H6).  In that case, they found that the
neutrons saw a ratio of hydrogen to carbon of 4.5 to 6!  Meanwhile,
this effect was also confirmed in various hydrogen-containing
metals, in a collaboration with Uppsala University in Sweden.
Now, the researchers (with new colleagues in Australia) have decided
to use an independent experimental method to verify this effect.  In
experiments at Australian National University in Canberra, the
researchers used electron probes instead of neutrons, as the two
particles interact with protons via fundamentally different forces
(strong and electromagnetic interactions).  Scattering electrons
from a solid polymer called formvar (with basic building block
C8H14O2),  they observed the exact same shortfall in scattered
electrons from hydrogen nuclei,  comparable to the shortfall of
scattered neutrons in accompanying neutron experiments on the same
polymer. This supports the earlier results on water and other
systems. (Chatzidimitriou-Dreismann et al., Physical Review Letters,
1 August 2003)

A NANOSCOPIC THERMOMETER, consisting of a magnesium oxide nanotube
filled with gallium metal, may dramatically increase the temperature
range of tiny thermometers. Researchers at the National Institute
for Materials Sciences (contact: Prof. Yoshio Bando, phone number
+81-29-860-4426; bando.yoshio{at}nims.go.jp ) announced the creation of
a carbon nanotube thermometer last year, but the device had at least
one shortcoming: nanoscopic carbon tubes rapidly degrade in air at
temperatures of 600-700 degrees Celsius. The new nanotubes are made
of magnesium oxide cylinders with inner diameters of 20-60
nanometers, or about a thousandth the thickness of a human hair.
Magnesium oxide nanotubes, in contrast to carbon versions, can
withstand high temperatures. Often, there is a gap in a nanotube's
gallium filling, and because gallium expands as it's heated, the
temperature of the thermometer is read out by measuring changes in
the gap between the two portions of the metal. The tiny thermometers
are expected to function well up to about 1000 degrees Celsius.
Eventually, miniature thermometers such as these could be important
for measuring temperature in the vicinity of nanoscopic motors and
other tiny devices. (Y.B. Li, Y. Bando, D. Golberg, and Z.W. Liu,
Applied Physics Letters, 4 August 2003)

***********
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