HR: 11:05h
AN: V41E-04    [PDF]
TI: Frontiers of High-Pressure Research: Synchrotron Infrared Spectroscopy
AU: * Liu, Z
EM: zxliu@bnl.gov
AF: Geophysical Laboratory, 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Mao, H
AF: Geophysical Laboratory, 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Hemley, R J
AF: Geophysical Laboratory, 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AB: High-pressure spectroscopy provides crucial and often unique information on the properties of Earth and planetary materials from near-surface conditions to those of the deepest interiors. Vibrational infrared/Raman spectroscopy, for example, provides detailed information on bonding properties of crystals, glass, and melts, thereby yielding a microscopic description of thermochemical properties. The high brightness of synchrotron infrared radiation is ideally suited to high pressure investigations in which both small sample area and a narrow beam are required in order to generate extremely high pressure with a diamond anvil cell. The dedicated high-pressure beam line U2A on the VUV ring of the National Synchrotron Light Source, Brookhaven National Laboratory is an integrated facility for a wide range of microspectroscopic studies from ambient to ultrahigh pressures and at variable temperatures. The beam line has high IR brightness, particularly at long wavelengths, with its 40 x 40 mrad aperture. The facility includes a FT-IR vacuum spectrometer (Bruker IFS 66v/S) along with a nitrogen purged high-pressure, long working distance microscopes for high pressure (and variable temperature) applications, a vacuum microscope system for far IR high-pressure absorption measurements and a commercial, high-magnification infrared microscope for diffraction-limited micro-infrared measurements of samples at ambient and high pressures. Recently, the beamline has been upgraded to further improve the performance in far-IR range. The facility thus permits systematic high-pressure studies addressing a range of problems in Earth and planetary science. These studies include high pressure (and variable temperature) studies of planetary gases and ices; minerals of the Earth's crust, mantle, and core; geochemical reactions; organic geochemistry; surfaces and interfaces and whole-rock samples; and extraterrestrial samples. These investigations complement optical laser spectroscopy, x-ray diffraction and spectroscopy, and transport measurements carried out on the same materials. High-pressure studies of various ices continue, with new phases being uncovered by these methods. New far-IR measurements have been carried out to test proposed pressure-induced phase transformations in ice at low temperature. These techniques have also been applied to biological molecules under pressure. Far-IR spectroscopy measurements down to 20 cm-1 have been used to characterize the low-frequency dynamics of model heme Fe-CO compounds, including the long-sought doming mode in which the iron atom moves out of the porphyrin plane. New single-crystal CVD diamond has been characterized from the far- to near-IR, including both as-grown and annealed material. The method has also been used to examine a variety of natural diamonds. Examples of recent experiments also include studies of hydrous mineral, such as gypsum, OH-clinohumite, and OH-chondrodite.
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 3994 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting