Showing papers on "Inorganic compound published in 1990"

Kinetic energy, temperature, and derived rotational temperature dependences for the reactions of Kr+(2P3/2) and Ar+ with HCl

Abstract: Rate constants for the reactions of Kr+(2P3/2) with HCl and DCl and of Ar+ with HCl have been measured as a function of reactant ion/reactant neutral average center‐of‐mass kinetic energy (〈KEc.m.〉 ) at several temperatures. The measurements were made using helium as the carrier gas. From these data we have derived the dependences of the rate constants on the rotational temperature of H(D)Cl. Rate constants for the reaction of Kr+(2P1/2) with HCl have also been measured as a function of temperature. The rate constants for all of the reactions were found to decrease with increasing temperature. The rate constants were also found to decrease with increasing 〈KEc.m.〉 at low 〈KEc.m.〉 but then to increase at higher 〈KEc.m.〉 . A significant rotational temperature dependence of the rate constant was derived for the reaction of Kr+(2P3/2) with H(D)Cl. The analogous derivation for Ar+ reacting with HCl showed the rate constant for this reaction to be independent of the rotational temperature of HCl within experimental uncertainty.

Nonlinear-optical susceptibilities of gases measured at 1064 and 1319 nm.

Abstract: The third-order nonlinear-optical susceptibilities of 16 simple atoms and molecules (Ne, Ar, Kr, Xe, ${\mathrm{H}}_{2}$, ${\mathrm{D}}_{2}$, ${\mathrm{N}}_{2}$, ${\mathrm{O}}_{2}$, ${\mathrm{CO}}_{2}$, ${\mathrm{CF}}_{4}$, ${\mathrm{SF}}_{6}$, ${\mathrm{CH}}_{4}$, ${\mathrm{C}}_{2}$${\mathrm{H}}_{6}$, ${\mathrm{C}}_{3}$${\mathrm{H}}_{8}$, n-${\mathrm{C}}_{4}$${\mathrm{H}}_{10}$, and ${\mathrm{C}}_{4}$${\mathrm{H}}_{6}$) have been measured in the gas phase at two near-infrared wavelengths using the technique of electric-field-induced second-harmonic generation (ESHG) with periodic phase matching and with He as the reference gas. These results are combined with previous ESHG data in the visible region to determine dispersion curves. The experimental estimate of the static hyperpolarizability \ensuremath{\gamma} for Ne, ${\ensuremath{\gamma}}_{\mathrm{Ne}}$=119\ifmmode\pm\else\textpm\fi{}3 a.u., is in good agreement with the best ab initio calculations, but the experimental estimates of the static hyperpolarizabilities for Ar and ${\mathrm{H}}_{2}$, ${\ensuremath{\gamma}}_{\mathrm{Ar}}$=1167\ifmmode\pm\else\textpm\fi{}20 a.u. and 〈${\ensuremath{\gamma}}_{\mathrm{H}2}^{\mathit{e}}$〉=686\ifmmode\pm\else\textpm\fi{}10 a.u., differ significantly from the best ab initio results.

Time-dependent superconducting behavior of oxygen-deficient YBa2Cu3Ox: Possible annealing of oxygen vacancies at 300 K.

Abstract: Oxygen stoichiometries in single crystals of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ are controlled by quenching from an ${\mathrm{O}}_{2}$-${\mathrm{N}}_{2}$ atmosphere at 520 \ifmmode^\circ\else\textdegree\fi{}C to liquid nitrogen. After quenching, the superconducting behavior and lattice parameters are found to be time dependent. ${\mathit{T}}_{\mathit{c}}$ increases as much as 15 K in a period of several days. Apparently, annealing, with increasing oxygen vacancy order, occurs at room temperature.

Comparison between calculated and experimental values of the lowest excited electronic state of small CdSe crystallites

Abstract: The lowest excited electronic state of small CdSe crystallites is calculated within a tight-binding approximation. Two types of crystal shape and a spatially varying dielectric constant are considered. The results are found to compare favorably to recent experiments.

Raman study of CuO single crystals.

Abstract: Raman scattering in single-crystalline CuO samples has been studied. From the polarization dependence, the symmetries of the three Raman-active optical phonons have been identified. The ${\mathit{A}}_{\mathit{g}}$ Raman mode with frequency of 290 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ was found to be strongly polarized along one of the crystal axes. This suggests that there are cancellations between different components of its Raman tensor.

Optical dielectric function and infrared absorption of hydrogenated amorphous silicon nitride films: Experimental results and effective-medium-approximation analysis.

Abstract: The optical dielectric function \ensuremath{\epsilon} (1.5--6.5 eV), ir absorption (400--4000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$), and film density have been measured for a series of hydrogenated amorphous silicon nitride (a-${\mathrm{Si}}_{\mathit{x}}$${\mathrm{N}}_{\mathit{y}}$${\mathrm{H}}_{\mathit{z}}$) films deposited at 400 \ifmmode^\circ\else\textdegree\fi{}C via rf plasma-enhanced chemical vapor deposition for varying [${\mathrm{NH}}_{3}$]/[${\mathrm{SiH}}_{4}$] ratios R. From a detailed analysis of the ir and density results, the concentrations of Si-N, N-H, Si-H, and Si-Si bonds and of Si, N, and H atoms have been obtained for the films studied. An effective-medium-approximation analysis of the measured \ensuremath{\epsilon} based on the Si-centered tetrahedron model presented in the preceding paper has provided a more sensitive means of determining the concentration of Si-Si bonds in the films and has demonstrated that careful measurements of ${\mathrm{\ensuremath{\epsilon}}}_{1}$ and ${\mathrm{\ensuremath{\epsilon}}}_{2}$ can serve as a useful probe of the bonding in these alloys. Approximately 9\ifmmode\times\else\texttimes\fi{}${10}^{20}$ Si-Si bonds/${\mathrm{cm}}^{3}$ have been found in N-rich films which are close in composition to silicon diimide, Si(NH${)}_{2}$, and these Si-Si bonds have been found to have a significant influence on both the optical energy gap ${\mathit{E}}_{\mathrm{opt}}$ and the refractive index n of the films. New results obtained from the ir absorption measurements include the identification of (1) a shoulder near 1030 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ on the main 880-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ Si-N(s) band and (2) a weak absorption feature near 640 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ which is not hydrogen related. It has been found that the N-rich diimidelike films prepared here have very low porosities and are thermally stable up to 700 \ifmmode^\circ\else\textdegree\fi{}C, properties which will be important for their future applications.

High temperature deformation of MoSi2 single crystals with the C11b structure

Abstract: Single crystals of MoSi2 with the C11b structure have been deformed in compression at 900–1500°C. Slip of the {013}〈3 3 1〉- and/or the {013}〈3 3 1〉- type is activated depending on crystal orientation. The critical resolved shear stress (CRSS) for {013}〈3 3 1〉- slip is much higher than that for {013}〈3 3 1〉- slip . At about 1300°C where ductility is remarkably improved, 〈100〉- and 〈110〉-type ordinary dislocations are observed and the climb mobility of these dislocations is very high. The CRSS for {013}〈3 3 1〉- slip , which depends on orientation exhibits a slight anomalous peak at 1000–1100°C. The anomalous strengthening is interpreted by the cross-slip mechanism as similar to that in L12 ordered alloys. Ductility improvement of MoSi2 above about 1200°C is assisted by the formation of stacking fault which is closely related to the instability of the C11b against to the C40 structure.

Extended X-ray absorption fine structure investigations of nickel hydroxides

Abstract: Etude de Ni(OH) 2 en phases α et β, a la temperature ambiante et a la temperature de l'azote liquide. Comparaison des longueurs des liaisons

Weak charge-transfer polyoxoanion salts: the reaction of quinolin-8-ol (Hquin) with phosphotungstic acid and the crystal and molecular structure of [H2quin]3[PW12O40]·4EtOH·2H2O

Abstract: Different solvated charge-transfer salts between quinolin-8-ol (Hquin) and phosphotungstic acid have been synthesized and characterized. Spectroscopic data support the presence of a sizeable electronic interaction between electron-rich aromatic organics and the inorganic acid, both in the solid state and in solution, provided that a large excess of the organic is present. This interaction is responsible for the formation of photosensitive compounds and provides a rationale for the subsequent facile photo-oxidation of the organic substrate. The crystal and molecular structure of [H2quin]3[PW12O40]·4EtOH·2H2O has been solved by the heavy-atom method and refined to a final R= 0.083, for 4 902 reflections with I 3σ(I): triclinic space group P; with a= 11.721(3), b= 12.818(3), c= 12.878(3)A, α= 89.20(2), β= 104.10(2), γ= 117.30(2)°, and Z= 1. The anion structure consists of an α-Keggin-type molecule in two-fold disorder. The 8-hydroxyquinolinium moieties (three per [PW12O40]3–) are stacked approximately along the x direction, with alternative interplanar spacings of 3.25 and 3.57 A. The crystal structure determination reveals the absence of any substantial, direct interaction between the organic cations and the phosphototungstate anions. Therefore no clear structural basis for the electronic interaction noted above can be given.