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31.
Semi-empirical molecular orbital calculations were carried out for the compounds (C2H5)3As, (C2H5)3Ga and RAsH2 (R = C2H5, i-C3H7, i-C4H9, and t-C4H9) by using the CNDO/2-U program, and their capability of β-elimination reaction is compared on the basis of the torsion energy to the transition state, electrostatic interactions and orbital overlapping between the central atom and the β-hydrogen, and bond order of the metal-carbon, and carbon-hydrogen bond. In the comparison of (C2H5)3As with (C2H5)3Ga, we found that the β-elimination of (C2H5)3As could hardly be expected to take place in the thermal decomposition. The capability of β-elimination would be smaller in C2H5AsH2 than that in (C2H5)3As. Moreover when the ethyl group is replaced by a t-butyl group in RAsH2, the β-elimination reaction appears to become more difficult and a large possibility for a radical process is suggested. 相似文献
32.
Ralf Jäger Anatolij I. Saprykin J. Sabine Becker Hans -Joachim Dietze José A. C. Broekaert 《Mikrochimica acta》1997,125(1-4):41-44
The analytical capabilities of a high-resolution mass spectrometer in combination with a 13.56 MHz glow discharge ion source for the analysis of semiconducting materials (silicon carbide and gallium arsenide) were studied. It was shown that single positively charged ions of sample material have about 10 eV higher average energy than the ions of the discharge and residual gas. Therefore effective energy separation of the ions of analyte from the ions of the discharge and residual gas was achieved by adjusting the ion transfer optics (breadth and position of energy slit), which improves the analytical capabilities of the developed method.Some analytical applications are presented to illustrate the performance of r.f. GDMS for the bulk analysis of semiconducting materials. The results of the trace element analysis of gallium arsenide and silicon carbide samples are compared with data of independent methods (LIMS, ICP-AES, SIMS).Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayOn leave from the Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia 相似文献
33.
Buffer gas beam coolers may become excellent beam preparation devices for high-resolution mass separation. The small beam
emittance provided makes efficient isobar resolution a realistic goal. In order to fulfill the needs of future facilities
providing high-intensity beams of rare isotopes, it is desirable to increase the beam intensity limit of such devices from
typically several tens of nanoamperes to microamperes. This requires the usage of high-voltage radiofrequencies in a low-pressure
gas environment. A buffer gas beam cooler, dedicated to this purpose, is under development at the NSCL. The study of voltage
breakdowns under such conditions and the design of an electrode system minimizing them is mandatory.
相似文献
34.
R. Németh 《Journal of statistical physics》1991,63(1-2):419-424
We calculate the site occupation probabilities of one-dimensional lattice gas models within the canonical and grand canonical ensembles. The appearing differences do not vanish if we increase the system size keeping the site energies discrete. In this way one can explain the surprising numerical results of Barszczak and Kutner. This effect in the single-site occupation number disappears in higher dimensions. 相似文献
35.
Modulated
DSC for gas hydrates analysis 总被引:1,自引:0,他引:1
C. Giavarini F. Maccioni Maria Laura Santarelli 《Journal of Thermal Analysis and Calorimetry》2006,84(2):419-424
Modulated DSC has been applied to the study of methane,
ethane and propane hydrates at different hydrate and ice concentrations. The
reversing component of the TMDSC curves, makes it possible to characterize
such hydrates.
Methane and ethane hydrates show the melting-decomposition
peak at a temperatures higher than the ice contained in the sample, while
propane hydrate melts and decomposes at lower temperature than the ice present
in the sample. The hydrate peaks tend to disappear if the hydrate is stored
at atmospheric pressure. Guest size and cavity occupation fix the heat of
dissociation and stability of the hydrates, as confirmed by parallel tests
on tetrahydrofurane hydrates. 相似文献
36.
This paper presents results of studies on dc electrical conductivity and transference number measurements on potassium bromate
(KBrO3) complexed polyvinyl chloride (PVC) films prepared by solution cast technique. Temperature dependence of dc electrical conductivity
and transference number data indicated the dominance of ion type charge transport in these specimens. The magnitude of conductivity
increased with increase in concentration of the salt and temperature. Using this (PVC + KBrO3) electrolyte, solid-state electrochemical cells were fabricated, and their discharge profiles were studied under a constant
load of 100 kΩ. Several cell profiles such as open circuit voltage, short circuit current, power density, and energy density
associated with these cells were evaluated and were reported. The features of complexation of the electrolytes were studied
by X-ray diffraction and Fourier transform infrared spectroscopy.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006 相似文献
37.
Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical DC glow
discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of
the discharge glow and shows a period subtraction of order 7 period → 5 period → 3 period → 1 period, i.e. the system goes
to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period
doubling, like 1 period → 2 period → 4 period. On further increasing the voltage, the system goes to stable state through
two period subtraction, like 4 period → 2 period → stable. 相似文献
38.
Summary The gas chromatographic behaviour of crosslinked macroporous 2-hydroxyethyl methacrylate grafted with 2-methyloxazoline was
investigated and the range of applicability of the copolymer was assessed. Retention index values were measured on this copolymer
and compared with those obtained on the terpolymer 2-hydroxyethyl methacrylate-ethylene dimethacrylate-acrylonitrile. Rohrschneider
constants and efficiency data for selected sorbates are given. The use of this type of polymer in the separation of various
types of compounds is documented by various examples. 相似文献
39.
40.