Diamond-Quality Properties

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.

However, Benedetti (925-424-5466, benedetti3@llnl.gov) 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).

Furthermore, JAP is published by the American Institute of Physics (AIP), which itself is celebrating its 75th anniversary in 2006 (http://www.aip.org/anniversary). (Journal of Applied Physics, upcoming article)