HR: 1330h
AN: V42A-0326    [PDF]
TI: Monitoring the Evolution of Electronic Band Gaps in Simple Molecules at High Temperature and Pressure
AU: * Furlanetto, M R
EM: m.furlanetto@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 United States
AU: Hemley, R J
EM: r.hemley@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 United States
AB: We present the first results from a new technique for tracking changes in electronic band gaps as a function of temperature, pressure, and wavelength in a diamond-anvil cell. We use the inner faces of the diamond anvils to form a Fabry-Perot interferometer, which allows us to measure the index of refraction of the sample as a function of pressure into the megabar range. By using ultrapure type IIa diamonds, we are able to monitor the index of refraction from the intrinsic band gap of diamond (5.5 eV or 240 nm) to the near infrared (1100 nm). Furthermore, by resistively heating the diamond-anvil assembly, we are able access a greater region of P-T space. The dispersion of the index of refraction is very sensitive to changes in electronic band structure, so we can map out the pressure-induced changes in the electronic band structure and use the temperature dependence of the dispersion to distinguish between direct and indirect band gaps. This technique has been applied to both ordered and disordered phases; as an example, we present preliminary results on the evolution of the band gaps of water, ice, solid, and fluid hydrogen.
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 3994 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting