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51.
52.
Tran H Joubert P Bonamy L Lavorel B Renard V Chaussard F Faucher O Sinardet B 《The Journal of chemical physics》2005,122(19):194317
With the aim of temperature diagnostic, femtosecond time-resolved CARS (coherent anti-Stokes Raman spectroscopy) is applied to probe H2 in H2-N2 mixtures. In a first part, a Lorentzian profile is used to model the femtosecond CARS response. A difference between the experimental broadening and the expected one is observed in the collision regime. The observed broadening increases strongly in an inhomogeneous way with respect to the perturber concentration. This is of considerable importance for temperature measurements. In a second part, we show that in the collision regime, this inhomogeneous broadening is due to the speed dependence of the collisional parameters and the memory effects of the radiator speed. A new modelization of the time-resolved CARS response taking into account the speed memory effects is presented and applied to the temperature diagnostic in H2-N2 mixtures. The numerical results are in good agreement with experiments. 相似文献
53.
Bhatia SK Tran K Nguyen TX Nicholson D 《Langmuir : the ACS journal of surfaces and colloids》2004,20(22):9612-9620
We present new simulation results for the packing of single-center and three-center models of carbon dioxide at high pressure in carbon slit pores. The former shows a series of packing transitions that are well described by our density functional theory model developed earlier. In contrast, these transitions are absent for the three-center model. Analysis of the simulation results shows that alternations of flat-lying molecules and rotated molecules can occur as the pore width is increased. The presence or absence of quadrupoles has negligible effect on these high-density structures. 相似文献
54.
Hai Pham Tuan Hans-Gerd Janssen Ellen M. Kuiper-van Loo Harm Vlap 《Journal of separation science》1995,18(9):525-534
Determination of trace concentrations of sulfur components in natural gas is a true analytical challenge. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. In the present contribution the sample pretreatment and chromatographic separation steps have been evaluated and optimized based on the use of a flamebased sulfur chemiluminescence detector (SCD) for target compound detection. The proposed instrument consists of a programmed temperature vaporizing (PTV) injector employing a liner packed with Chromosorb 104, a 4 μm thick film apolar column and a flame-based SCD. Using a 13 mL sample loop the detection limit achievable with the new method is 3 μg S/m3. The precision of replicate measure. ments is generally in the range of 5–15% relative standard deviation. Lower detection limits can be achieved by preconcentrating larger sample volumes, e.g. 100 mL. 相似文献
55.
Single crystal structure determinations prove the two pyridine substituents in di(2-pyridyl)ketone (H4C4NC)2C=O to be twisted out of the carbonyl skeleton plane by torsion angles (OCCN) of 41° and –163°, in contrast to their planar arrangement in azo-di(2-pyridine) H4C4NC)-N=N-(CNC4H4). In order to rationalize the surprising difference between the two isoelectronic molecules, approximate PM3 enthalpy of formation hypersurfaces have been calculated for each of the two ring torsions, which are assumed to be the dominant ones among the 3N – 6 = 60 degrees of freedom. For both the ketone and the azo derivative, global minima are calculated, the torsion angles of which deviate from the crystal structure results, and, therefore, support the assumption that both the experimentally determined twisting of di(2-pyridyl)ketone as well as the flattening of azo-di(2-pyridine) might be affected by the crystal packing. 相似文献
56.
Feng Xian Liu-Cai Charlotte Pham Farida Bey Gilbert Hervé 《Reaction Kinetics and Catalysis Letters》2002,75(2):305-314
Effects of Cs+, H+ and Cu2+ counterions in the vanadium containing heteropoly compounds CsxH1-xVO[PMo12O40] and CsyH0.5-yCu0.25VO[PMo12O40] on the catalytic oxidation of isobutane and characterization by TGA, IR and ESR spectroscopies are reported. A high selectivity of 76% for methacrylic acid and methacrolein together has been obtained with Cs0.75H0.25VO[PMo12O40] catalysts at a reactivity of 5.3x10-1 mmol/h cm3. 相似文献
57.
Brigitte Florin-Michel Marie-France Llauro R. Spitz Q.-T. Pham 《European Polymer Journal》1979,15(3):277-283
Ethylene 1-hexene copolymers obtained by catalytic polymerization have been examined by 1H and 13C NMR. Copolymer compositions have been determined by 1H NMR and i.r. and the sequence distributions for 1-hexene by 13C NMR. Variations of the copolymer microstructure have been related to the experimental conditions for copolymerization. 相似文献
58.
Synthesis and spectral characterization of some complexes of platinum(II) containing η-methyleugenol
Several complexes of the formula trans-[Pt(Meug)(Am)Cl2], Meug: methyleugenol (4-allyl-1,2-dimethoxybenzene), a η2-coordinated olefin, and Am: ammine, methylamine, diethylamine, o-toluidine, m-toluidine, p-toluidine, o-anisidine, m-anisidine and p-anisidine have been prepared. UV, IR, Raman, 1H NMR, 13C NMR and 2D NMR spectra of the complexes were recorded and analyzed. 相似文献
59.
[reaction: see text] Three novel domino reaction processes have been discovered and developed that employ the regioselective and stereoselective [Rh(CO)(2)Cl](2)-catalyzed alkylations of allylic trifluoroacetates with alpha-substituted sodiomalonates followed by an intramolecular Pauson-Khand annulation, a [5 + 2] cycloaddition, or a cycloisomerization. A unique aspect of the methodology is that a single catalyst is used to effect sequential transformations simply by increasing the temperature for the second reaction. 相似文献
60.
Proton affinities of a series of triphenyl Group Va compounds have been determined by bracketing using reactant ion monitoring: (C6H5)3N = 904 ± 8 kJ mol?1, (C6H5)3P = 968 ± 5 kJ mol?1, (C6H5)3As = 904 ± 8 kJ mol?1 and (C6H5)3Sb = 846 ± 8 kJ mol?1. The large difference in substituent effect of phenyl for hydrogen between As or P and N may result from overlap of the 2p orbitals of N with the sp2 orbitals on the ring carbons and lack of overlap for P or As. Proton affinities of phenylalkylphosphine oxides are essentially the same, 904 ± 8 kJ mol?1, independent of alkyl group. 相似文献