Number 806 #2, December 20 , 2006 by Phil Schewe, Ben Stein, and Davide Castelvecchi
Much of what we know about how materials
behave under extreme pressures and temperatures (millions of
atmospheres and thousands of Kelvin) is learned using diamond anvil
cells. In these tiny enclosures, material can be squeezed between
the flat, hard, transparent faces of two gem quality diamonds. Because
diamond is transparent over much of the electromagnetic spectrum, many types of radiation, such
as laser beams or light emitted from or scattered by the sample
(light containing valuable spectroscopic information) can enter and
exit through the diamond windows.
However, the diamond itself can
introduce subtle optical distortions, and some physicists believe
experimenters need to take a closer look at two important
parameters: dispersion (the optical property that gives diamonds
their "fire"; appearance) and absorbance. Both of these parameters
are crucial for spectro-radiometry (the determination of the
temperature by spectroscopic methods) of samples contained in the
diamond anvil cell.
Laura Robin Benedetti and Daniel Farber of the
Livermore National Lab and Nicolas Guigot of the European
Synchrotron Radiation Facility believe that by not taking into
account the effects of dispersion and absorbance, experimenters can
introduce errors in measured temperatures (typically in the
1500-4000 K range) of as much as several hundred Kelvin.
Benedetti (925-424-5466, email@example.com) says that their new
work presents ways of compensating for the distortions introduced by
the optical properties of the diamond windows. It's appropriate that
this new look at diamonds appears in the Journal of Applied Physics
(JAP), which this year marks its diamond anniversary (http://jap.aip.org/jap/top.jsp).