HIGH-PRESSURE SYNCHROTRON INFRARED-SPECTROSCOPY AT THE NATIONAL SYNCHROTRON LIGHT-SOURCE

We describe a synchrotron infrared facility for high-pressure spectros copy and microspectroscopy at the National Synchrotron Light Source (N SLS). Located at beamline U2B on the VUV ring of the NSLS, the facilit y utilizes a commercial FT-IR together with custom-built microscope op tics designed for a variety of diamond anvil cell experiments, includi ng low- and high-temperature studies. The system contains an integrate d laser optical/grating spectrometer for concurrent optical experiment s. The facility has been used to characterize a growing number of mate rials to ultrahigh pressure and has been instrumental in the identific ation of new high-pressure phenomena. Experiments on dense hydrogen to > 200 GPa have led to the discovery of numerous unexpected properties of this fundamental system. The theoretically predicted molecular-ato mic transition of H2O ice to the symmetric hydrogen-bonded structure h as been identified, and new classes of high-density clathrates and mol ecular compounds have been characterized. Experiments on natural and s ynthetic mineral samples have been performed to study hydrogen speciat ion, phase transformations, and microscopic inclusions in multiphase a ssemblages. Detailed information on the behavior of new materials, inc luding novel high-pressure glasses and ceramics, has also been obtaine d.