Fundamental and combination bands of CO2–C2H2 and CO2–C2D2 in the mid-infrared region

Spectra of the weakly bound CO₂–C₂H₂ and CO₂–C₂D₂ complexes are observed in the regions of CO₂ ν₃ (≈ 2349 cm^?1) and C₂D₂ ν₃ (≈ 2440 cm^?1) fundamental vibrations, using an infrared optical parametric oscillator to probe a pulsed supersonic slit-jet expansion. Five bands are measured and analysed: the fundamental asymmetric stretch of the C₂D₂ component, two combination bands involving the out-of-plane torsional vibrations (C₂D₂ ν₃ + torsion and CO₂ ν₃ + torsion) for CO₂–C₂D₂, and two combination bands involving an intermolecular in-plane bending vibration for CO₂–C₂H₂ and CO₂–C₂D₂. The resulting intermolecular frequencies are 61.408(1), 54.5(5), 39.9(5), and 39.961(1) cm^?1 for CO₂–C₂H₂ and CO₂–C₂D₂ in-plane vibrations, and CO₂–C₂D₂ out-of-plane torsional vibrations in CO₂ and C₂D₂ regions, respectively. This is the first experimental determination of these intermolecular vibrational frequencies.     

Molecular structure of cyclopropenylidene,HCCCH from the millimeter wave spectra of its isotopomers

The rotational spectra of the two ¹³C and of the D monoisotopic substitutions of cyclopropenylidene C₃H₂ have been measured up to 300 GHz. The determination of the rotational and centrifugal distortion constants of four isotopomers has led to a complete substitution structure. The values of the two CC bond lengths which define the three-membered ring have been improved by using Watson's “mass-dependence” (r_m) method.     

Thermodynamics and phase diagrams of MoPdRu and related systems

During the irradiation of nuclear fuels up to 10% of the original fissile material (uranium and plutonium) is converted into a wide range of fission products. One particular group of fission-product elements, the transition metals Mo, Tc, Ru, Rh and Pd, are not oxidised at the quite low oxygen potentials existing in the fuels, and are precipitated in the fuel in the form of metallic inclusions. The thermodynamic properties and phase diagram of these alloys are of importance, since the precise composition of these alloys, as a function of radial position can provide important information concerning operating conditions inside a fuel pin. For this reason a thorough reassessment of these systems is under way. This paper reports values of the excess-Gibbs energies of mixing in the MoPd, PdRu and MoRu binary systems, and in the MoPdRu ternary. Calculated sections of the MoPdRu system at selected temperatures are presented.     

The superconductivity,structure and microstructure of BaYScCu oxides

We added small amount of Sc (0.05–0.35at.%) to BaYCu oxide and found that the superconductivity deteriorated drastically when the Sc content reached 0.325at.%. X-ray and electron diffraction showed that the orthorhombic perovskite structure changed to multi-phase structure with unidentified phases. The microstructures observed by TEM are of needle like morphology. Their phases are not yet identified.     

Lattice dynamics and debye temperature of AlCu,AlSi and AlGe alloy systems

The lattice dynamics and specific heat at constant volume for AlCu alloy system is studied using our previous treatment based on the microscopic electronic theory. Considering the volume and electron density effect on the dynamical matrix of the pure constituent, we obtain the band and local mode frequencies at the temperature-dependent specific heat in the Al_1−x Cu_x solid solution. Then, using the data about the mean elastic wave and the specific heat extrapolated to the absolute zero temperature, the Debye temperature is presented for the Al_1−xCu_x, Al_1−xSi_x and Al_1−xGe_x alloy systems. The Debye temperature decreases as a function of the Cu atomic fraction x for Al_1−xCu_x alloy, and remarkably for Al_1−xSi_x and Al_1−xGe_x solid solutions.     

Oxide-supported metals with molecular structures: Evidence of the metal-oxygen bond from Raman and inelastic electron tunneling spectra of [Re(CO){in3}{OMG}{HOMg}2] and [Re(CO)3{OAl}{HOAl}2]

Raman and inelastic electron tunneling spectra of the anchored rhenium complexes [Re(CO){in3}{OMG}{HOMg}₂] and [Re(CO)₃{OAl}{HOAl}₂] are reported, providing the first vibrational spectroscopic evidence of the metal-oxygen bond in mononuclear oxide-bound organometallic complexes.     

Anisotropy of the superconducting critical magnetic field HC2 of LaMCuO system(M = Sr and Ba)

Preliminary measurement of the superconducting critical magnetic field H_c2 of LaMCuO system (M = Sr and Ba) with layered perovskite structure has been carried out. The results show a quite large anisotropy of H_c2 indicating that the present system has a two dimensional character of the electron transport. The measured conductivities seem to be consistent with the values estimated from the observed H_c2 by use of an ideal two dimensional band with free electron mass.     

Modeling the phase equilibria of a H2O–CO2 mixture with PC-SAFT and tPC-PSAFT equations of state

Water–carbon dioxide binary mixtures are important for a number of industrial and environmental applications. Accurate modeling of the thermodynamic properties is a challenging task due to the highly non-ideal intermolecular interactions. In this work, two models based on the Statistical Associating Fluid Theory (SAFT) are used to correlate reliable experimental vapor–liquid equilibria (VLE) and liquid–liquid equilibria (LLE) data in the temperature range 298–533?K. CO₂ is modeled as a non-associating or associating component within the Perturbed Chain-SAFT (PC-SAFT) and as a quadrupolar component within the truncated PC-Polar SAFT (tPC-PSAFT). It is shown that PC-SAFT with explicit account of H₂O–CO₂ cross-association and tPC-PSAFT with explicit account of CO₂ quadrupolar interactions are the most accurate of the models examined. Saturated liquid mixture density data are accurately predicted by the two models.     

Dynamical behaviour of PtRh(100) alloy surface during dissociative adsorption of NO and reaction of NO with H2

When a clean Pt-Rh(100) alloy surface was exposed to NO at T > 440 K, the LEED pattern changed sequentially as p(1 × 1) → c(2 × 2) → c(2 × 2) + p(3 × 1) → p(3 × 1), where the c(2 × 2) pattern appeared immediately after the exposure to NO. In contrast to this, the appearance time for the p(3 × 1) depends strongly on the initial Rh concentration on the surface adjusted by annealing. When the p(3 × 1) surface was exposed to H₂ by mixing H₂ into NO gas, the AES intensity of O(a) decreased and of N(a) increased markedly and the LEED pattern changed from p(3 × 1) to c(2 × 2). These results suggest that N(a) has equal affinity to Pt and Rh atoms so that the N(a) does not distinguish the Pt and Rh sites on the alloy surface. On the other hand, O(a) makes a stronger bond with Rh atoms so that Rh atom segregation onto the surface is induced. By reacting randomly distributed Rh atoms on the Pt-Rh(100) surface with oxygen, a surface compound in a p(3 × 1) arrangement is built on the surface.     

Electron diffraction and electron microscopic study of BaYCuO superconducting materials

Electron microscopy and electron diffraction have been applied to show that the orthorhombic phase in the compound Ba₂YCu₃O_7−δ is responsible for the high superconducting transition temperature. A positive correlation is found between the volume fration of the orthorhombic phase and the superconducting transition temperature. By means of an “in-situ” heating experiment it is found that the orthorhombic phase is formed on cooling from a high temperature tetragonal phase with disordered vacancies. It is suggested that the low temperature tetragonal phase that occurs in the same specimens as the orthorhombic phase also contains an ordered arrangement of vacancies different from that present in the orthorhombic phase. The order-disorder transition associated with the structural vacancies is shown to be reversible, provided there has been no oxygen loss.     

Oscillatory behaviour of the NOH2 reaction over Rh(533)

Waves moving over the surface of a Rh field emitter tip in an oscillatory way during the NO-H₂ reaction have been visualized earlier by field electron microscopy (FEM). An autocatalysis model has been proposed to describe the oscillatory behaviour of the reduction of NO by H₂. To study the oscillatory behaviour and the effect of the surface structure in more detail a large Rh(100) surface and a large stepped Rh(533) surface, Rh[4(111)¹(100)], have been selected. The first results show that, in correspondence with the FEM experiments, rate oscillations could be observed over the Rh(533) surface in the 10⁻⁶ mbar pressure regime around 470 K. No oscillatory behaviour was obtained on the Rh(100) surface under these conditions. The structure-sensitivity of the process is related to the large dependence of the Rh-N bond strength on the surface structure. Nitrogen desorbs at a much higher temperature from Rh(100) than from Rh(533).     

CO laser-microwave double-resonance spectroscopy of H2CO with intense Stark field: Precise measurement of dipole moment in the ground and ν2 vibrational states

Stark-shifted microwave transitions in the ground and ν₂ vibrational states of H₂CO were observed by means of CO laser-microwave double-resonance with intense electric field. High sensitivity and precision were attained by the use of multireflection absorption cell, optical-flat Stark plates, and microwave frequency stabilization. Dipole moments determined from some individual rotational transitions in the ground and ν₂ vibrational states are, in Debye, with uncertainties in parentheses,

     

19.

X-ray photoemission studies of PtSn and PtPb bimetallic systems     

《Surface science》1986,177(3):493-514

The Pt(5d) and Pt(4f) in PtSn and PtPb composites produced by sequential vapor deposition have been examined by X-ray photoelectron spectroscopy. At low concentrations of Pt, the Pt(5d) becomes a single, narrow resonance at about 4 eV below the Fermi level. Its density of states at the Fermi level is small. This leads to a large suppression of the Pt(4f) lineshape asymmetry. As the Pt concentration increases, d-d interactions split the Pt(5d) resonance and increase the 5d density of states at the Fermi level by pushing one of the split resonances to the Fermi level. Consequently, the Pt(4f) lineshape asymmetry increases. The evolution of the Pt(4f) and Pt(5d) in PtSn and PtPb are very similar but different from that of small Pt particles supported on carbon. The close similarity of the electronic properties of Pt in PtSn and PtPb suggests that the poisoning of Pt by Pb is not entirely due to electronic effects although there are indications of stronger interaction between Pt and Pb than between Pt and Sn atoms. The strong surface enrichment of Pb on PtPb points to the importance of the physical blockage of Pt atoms by surface Pb in determining the poisoning effect of Pb.     

20.

Vibration-rotation spectrum of formaldehyde: CH stretching fundamentals ν1 and ν5     

Toru Nakagawa  Koichi Yamada  Kozo Kuchitsu 《Journal of Molecular Spectroscopy》1976,63(3):485-508

The infrared vibration-rotation spectrum of formaldehyde vapor has been measured in the region from 2600 to 3400 cm^?1 with resolution from 0.04 to 0.07 cm^?1. An extensive rotational analysis of the ν₁ and ν₅ bands has confirmed and superseded the previous band-contour analysis of a medium-resolution spectrum. A large number of subbranches of both the ν₁ and ν₅ bands are perturbed by the combination bands ν₃ + ν₆, ν₂ + ν₄, and ν₂ + ν₆, whereas the Coriolis interaction between ν₁ and ν₅ is weak. The following effective rotational constants (in cm^?1) are obtained:

$\text{ν}{}_1\text{= 2782.49(1), A}{}_1\text{= 9.250(5), B}{}_1\text{= 1.2968(6), C}{}_1\text{= 1.1321(2)}$

,

$\text{ν}{}_0\text{= 2843.35(2), A}{}_0\text{= 9.224(2), B}{}_0\text{= 1.2936(2), C}{}_0\text{= 1.1303(1)}$

, where the number given in parentheses is three times the standard error in the last digit.     

Transition		G.S.		$\text{ν}{}_2$		δμ
110 ← 111		2.3315 (1)		2.3472 (1)		0.0157 (1)
211 ← 212		2.3313 (1)		2.3471 (1)		0.0158 (1)
312 ← 313		2.3313 (1)		2.3470 (1)		0.0157 (1)
826 ← 827		2.3311 (1)		2.3466 (1)		0.0155 (1)
927 ← 928		—		2.3466 (1)		—

X-ray photoemission studies of PtSn and PtPb bimetallic systems

The Pt(5d) and Pt(4f) in PtSn and PtPb composites produced by sequential vapor deposition have been examined by X-ray photoelectron spectroscopy. At low concentrations of Pt, the Pt(5d) becomes a single, narrow resonance at about 4 eV below the Fermi level. Its density of states at the Fermi level is small. This leads to a large suppression of the Pt(4f) lineshape asymmetry. As the Pt concentration increases, d-d interactions split the Pt(5d) resonance and increase the 5d density of states at the Fermi level by pushing one of the split resonances to the Fermi level. Consequently, the Pt(4f) lineshape asymmetry increases. The evolution of the Pt(4f) and Pt(5d) in PtSn and PtPb are very similar but different from that of small Pt particles supported on carbon. The close similarity of the electronic properties of Pt in PtSn and PtPb suggests that the poisoning of Pt by Pb is not entirely due to electronic effects although there are indications of stronger interaction between Pt and Pb than between Pt and Sn atoms. The strong surface enrichment of Pb on PtPb points to the importance of the physical blockage of Pt atoms by surface Pb in determining the poisoning effect of Pb.     

Vibration-rotation spectrum of formaldehyde: CH stretching fundamentals ν1 and ν5

The infrared vibration-rotation spectrum of formaldehyde vapor has been measured in the region from 2600 to 3400 cm^?1 with resolution from 0.04 to 0.07 cm^?1. An extensive rotational analysis of the ν₁ and ν₅ bands has confirmed and superseded the previous band-contour analysis of a medium-resolution spectrum. A large number of subbranches of both the ν₁ and ν₅ bands are perturbed by the combination bands ν₃ + ν₆, ν₂ + ν₄, and ν₂ + ν₆, whereas the Coriolis interaction between ν₁ and ν₅ is weak. The following effective rotational constants (in cm^?1) are obtained:

$\text{ν}{}_1\text{= 2782.49(1), A}{}_1\text{= 9.250(5), B}{}_1\text{= 1.2968(6), C}{}_1\text{= 1.1321(2)}$

,

$\text{ν}{}_0\text{= 2843.35(2), A}{}_0\text{= 9.224(2), B}{}_0\text{= 1.2936(2), C}{}_0\text{= 1.1303(1)}$

, where the number given in parentheses is three times the standard error in the last digit.