FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

Extensive new high-temperature, high-resolution FTIR emission spectroscopy measurements for the five common isotopomers of GeO are combined with previous diode laser and microwave measurements in combined isotopomer analyses. New Dunham expansion parameters and an accurate analytical potential energy function are determined for the ground X1Sigma+ state. Copyright 1999 Academic Press.     

On the shape of the Q-branch of Raman scattering spectra in dense media. Theory

A nonadiabatic quasi-classical impact theory of the Q-band shape for isotropic and anisotropic Raman scattering by linear rotors has been developed. With our previous results this allows us to obtain upper and lower estimates of the contribution of collisional rotational relaxation to the Raman line broadening.     

Solvent effect on catalytic properties of the HCI-DMF-1,1,2,2-tetrachloroethane system

Ionization of 2- and 3-nitroanilines was studied in HCl-DMF-1,1,2,2-tetrachloro-ethane (TCE) solutions at 25 °C. The ionization capability of the medium and basicity constants pK _i of indicators change depending on the ratio of the components. The numerical values of pK _i are found to depend on the analytical composition of the DMF-TCE solvent. The solvent effect on pK _i is associated with a change in the solvation of the nonionized form of the indicators.Translanted fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1446–1449, June, 1996.     

Effect of 1,1,2,2-tetrachloroethane on the ionizing ability of complexes of HCl with DMF

The acidity function (H _o) of solutions of HCI (0–7.1 mol L^?1) in an equimolar mixture of DMF-1,1,2,2-tetrachloroethane (TCE) has been determined by the indicator method at 25 °C. Data on the relative ionizing activity of complexes of HCI with DMF with various compositions and structures have been obtained. In the ternary system HCI-DMF-TCE, the ionizing ability of the complexes of DMF with HCI of the compositions 2 : 1 and 1 : 1 with a quasiionic structure decreases compared to the HCI-DMF system, and that of the complex of the composition DMF · 2HC1 with a structure of an ion pair Me₂NHCOH⁺ · (CIHCI)^? with a strong centrosymmetrical H-bond in the anion increases.     

Palladium(<Emphasis Type="SmallCaps">I</Emphasis>) and palladium(0) carbonyl bromide complexes

New Pd^I and Pd⁰ carbonyl bromide complexes co-existing in the same crystal were synthesized and studied by X-ray diffraction analysis. The crystals consist of dimeric complex anions composed of the central Pd(μ-CO)₂Pd fragment and four partially disordered terminal ligands (CO and Br⁻). The complexes were characterized by IR, ESR, and X-ray photoelectron spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1349–1355, June, 2005.     

Mechanism of oxidative carbonylation of phenylacetylene and methylacetylene. Generation and experimental discrimination of hypotheses

Formal and informal methods for advancing hypotheses on mechanisms were used in a study of the oxidative carbonylation of phenylacetylene to methyl phenylpropiolate catalyzed by the PdCl₂−CuCl−CuCl₂ system. The hypotheses remaining after discrimination and consistent with all experimental data include the steps of formation of the Cu^I alkynyl complex, transfer of the phenylethynyl group from Cu^I to Pd^II, insertion of carbon monoxide into a Pd−C or Pd−OMe bond of the Pd^II σ-alkynyl complex. Comparison of the formal and informal methods for advancing hypotheses confirmed a higher effeciency of the first method. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 882–889, May, 1999.     

New catalytic systems for oxidative carbonylation of acetylene to maleic anhydride

A classification of polyfunctional catalytic systems based on discrimination of the main component (the catalyst participating in all stages of the formation of the product of catalytic reaction) and elucidating the functions of additional components of a catalytic system is suggested. The role of additional components in a number of new palladium-based catalytic systems used in the synthesis of maleic anhydride by oxidative carbonylation of acetylene was studied. It was established that the functions of Co and Fe phthalocyanine complexes (PcCo and Pc^*Fe, respectively) in the mechanism of the process are different. Translated fromIzvestia Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1899–1905, October, 1999.     

Electromagnetic Analysis and Cold Test of a Distributed Window for a High Power Gyrotron

A novel distributed window for output radiation from a high power 110 GHz gyrotron is made of thin slats of sapphire interleaved and brazed to hollow metal vanes. We report the results of electromagnetic theory and cold test of this distributed window. We calculate the frequency dependence of the reflectivity of a Gaussian beam from the window. The theory indicates a significant frequency shift of the minimum reflectivity with temperature rise of the sapphire slab. This effect is of great importance for high power operation. In cold test, the distributed window reflectivity was measured while the window was heated. The cold test results are in good agreement with the theory.     

Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source

In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g=2 electrons, 380 MHz for 1H). In these experiments, 1H enhancements of up to 170+/-50 have been observed in 1-13C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20K; in addition, we have observed significant enhancements in 15N spectra of unoriented pf1-bacteriophage. Finally, enhancements of approximately 17 have been obtained in two-dimensional 13C-13C chemical shift correlation spectra of the amino acid U-13C, 15N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments.