Spectroscopy at very high pressures. X. Use of ruby R-lines in the estimation of pressure at ambient and at low temperatures

Luminescent copper(i) complexes with bisphosphane and halogen-substituted 2,2′-bipyridine ligands

Light-emitting electrochemical cells with Cu(i) emitters with halo-substituted 2,2′-bipyridine ligands display orange electroluminescence and short turn-on times.

Copper(i) and silver(i) complexes of 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene: photophysical properties and structural rigidity under pressure

Structural, photophysical and electrochemical properties of heteroleptic copper(i) and silver(i) complexes [M(tBu-xantphos)(bpy)][PF₆] are described where tBu-xantphos is 4,5-bis(di-tert-butylphosphino)-9,9-dimethylxanthene.

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

The numerical coefficients linearly relating the effects of stress (including pressure), temperature, and composition to shifts in the energies of the Cr-related fluorescence in alumina (Al₂O₃) are reviewed. The primary focus is the shift of the R₁ and R₂ "ruby" fluorescence lines under conditions typical for stress determination in polycrystalline Al₂O₃. No significant experimental difference in the R₁ and R₂ responses is observed for hydrostatic stress (or pressure) conditions (average shift coefficient of about 7.6 cm^-1/GPa), changes in temperature (about 0.140 cm^-1/K), or variations in composition (about 120 cm^-1/mass fraction of Cr). There are significant differences in the R₁ and R₂ responses for nonhydrostatic stress conditions. In particular, for uniaxial stress along the a and c directions in the Al₂O₃ crystal, the R₁ piezospectroscopic tensor coefficients (about 3.0 cm^-1/GPa and 1.6 GPa cm^-1/GPa, respectively) differ considerably, whereas the R₂ coefficients (about 2.6 cm^-1/GPa and 2.3 GPa cm^-1/GPa, respectively) do not. Measurements of the piezospectroscopic tensor coefficients are shown to have interlaboratory relative consistency of about 4 % extending over 30 years, and are consistent with the scalar high-pressure measurements. Measurements of the temperature coefficients are shown to have interlaboratory relative consistency less than 1 % extending over 60 years. Fluorescence-based measurements of stress in polycrystalline Al₂O₃, although requiring temperature adjustment, are shown to have a relative uncertainty of about 2.5 %.

Evaluations of pressure-transmitting media for cryogenic experiments with diamond anvil cell

The fourteen kinds of pressure-transmitting media were evaluated by the ruby fluorescence method at room temperature, 77 K using the diamond anvil cell (DAC) up to 10 GPa in order to find appropriate media for use in low temperature physics. The investigated media are a 1:1 mixture by volume of Fluorinert FC-70 and FC-77, Daphne 7373 and 7474, NaCl, silicon oil (polydimethylsiloxane), Vaseline, 2-propanol, glycerin, a 1:1 mixture by volume of n-pentane and isopentane, a 4:1 mixture by volume of methanol and ethanol, petroleum ether, nitrogen, argon, and helium. The nonhydrostaticity of the pressure is discussed from the viewpoint of the broadening effect of the ruby R(1) fluorescence line. The R(1) line basically broadens above the liquid-solid transition pressure at room temperature. However, the nonhydrostatic effects do constantly develop in all the media from the low-pressure region at low temperature. The relative strength of the nonhydrostatic effects in the media at the low temperature region is discussed. The broadening effect of the ruby R(1) line in the nitrogen, argon, and helium media are significantly small at 77 K, suggesting that the media are more appropriate for cryogenic experiments under high pressure up to 10 GPa with the DAC. The availability of the three media was also confirmed at 4.2 K.

Remote Raman and fluorescence studies of mineral samples

In the present study, we investigated remote laser-induced fluorescence (LIF), at a distance of 4.8 m, of a variety of natural minerals and rocks, and Hawaiian Ti (Cordyline terminalis) plant leaves. These minerals included calcite cleavage, calcite onex and calcite travertine, gypsum, fluorapatite, Dover flint and chalk, chalcedony and nephelene syenite, and rubies containing rock. Pulsed laser excitation of the samples at 355 and 266 nm often resulted in strong fluorescence. The LIF bands in the violet-blue region at approximately 413 and approximately 437 nm were observed only in the spectrum of calcite cleavage. The green LIF bands with band maxima in the narrow range of approximately 501-504 nm were observed in the spectra of all the minerals with the exception of the nephelene syenite and ruby rocks. The LIF red bands were observed in the range approximately 685-711 nm in all samples. Excitation with 532 nm wavelength laser gave broad but relatively low fluorescence background in the low-frequency region of the Raman spectra of these minerals. One microsecond signal gating was effective in removing nearly all background fluorescence (with peak at approximately 610 nm) from calcite cleavage Raman spectra, indicating that the fluorescence was probably from long-lifetime inorganic phosphorescence.

Pressure induced phase transitions in hydroquinone

High pressure behavior of alpha-hydroquinone (1,4-dihydroxybenzene) has been studied using Raman spectroscopy up to pressures of 19 GPa. Evolution of Raman spectra suggests two transitions around 3.3 and 12.0 GPa. The first transition appears to be associated with the lowering of crystal symmetry. Above 12.0 GPa, Raman bands in the internal modes region exhibit continuous broadening suggesting that the system is progressively evolving into a disordered state. This disorder is understood as arising due to distortion of the hydrogen-bonded cage across the second transition around 12 GPa.

Magnetic properties of hexagonal closed-packed iron deduced from direct observations in a diamond anvil cell

The attraction of hexagonal closed packed (hcp) iron to a magnet at 16.9 gigapascals and 261 degrees centigrade suggests that hcp iron is either paramagnetic or ferromagnetic with susceptibilities from 0. 15 to 0.001 and magnetizations from 1800 to 15 amperes per meter. If dominant in Earth's inner core, paramagnetic hcp iron could stabilize the geodynamo.

Uniform stress conditions in the diamond anvil cell at 200 kilobars

Pressure gradients in a diamond anvil cell have been measured with a 4:1 methanol:ethanol mixture as a pressure medium up to 350 kilobars. When pressure is applied rapidly, stress gradients are shown to be negligible up to 200 kilobars and probably above. With this procedure it is possible to significantly increase the precision of pressure measurements above 100 kilobars.

Viscosity measurements in the diamond anvil pressure cell

The viscosity of liquids can be measured in the diamond-anvil pressure cell utilizing a falling-solid sphere method and the ruby technique for pressure measurement. The pressure dependence of the viscosity of a 4:1 mixture (by volume) of methanol-ethanol was determined to 70 kilobars. The accuracy of the method is estimated from measurements made on a fluid of known viscosity.

Spectroscopy at very high pressures. 14: Laser Raman scattering in ultrasmall samples in a diamond anvil cell

The problem of obtaining Raman spectra at high pressures with a diamond anvil cell is analyzed, and the successful use of a 90 degrees off-axis ellipsoidal mirror for collection in both 0 degrees and 180 degrees scattering modes is demonstrated with nu(OH) spectra of ice VI, VII, and vIII.