A new method is introduced for imaging microwave fields, such as those found in microwave-plasma support structures. The method relies upon the darkening that such fields cause in heat-sensitive paper, such as that used in some telefax printers. With this new method, the microwave-frequency electric fields inside two microwave-plasma support structures, the surfatron and the microwave plasma torch, have been measured and subsequently imaged in three dimensions. The images reveal that the surfatron and microwave plasma torch have different operational behavior. As expected, the electric field strength inside the surfatron exponentially falls off down the length of the quartz plasma tube. The field inside the microwave plasma torch initially diminishes, but then increases in strength towards the end of the tube. An aerosol was introduced into the surfatron to observe the effect of water vapor on the electric field strength and distribution. The exponential axial decay of the electric field in the ‘dry’ surfatron plasma, characteristic of a surface wave propagating down a quartz plasma tube, is extended further down the quartz tube in the ‘wet’ plasma. A drop in plasma conductivity is likely the origin of the elongated propagation of the surface wave. 相似文献
Journal of Thermal Analysis and Calorimetry - Microwave-assisted formulation is becoming an established method of formulation in industry, providing a fast, economic and environmentally more... 相似文献
The microwave spectrum of tellurophene, C4H4Te, has been recorded between 8 and 27 GHz. The rotational constants obtained from least-squares fitting of low-J lines are: Figures in parentheses are uncertainties in last place of decimal (95% confidence limit). Corresponding inertial defects are 0.094 (7), 0.095 (6) and 0.097 (10) amu A2 respectively, indicating the essential planarity of the molecule.Stark shift measurements correspond to a dipole moment of μa = 0.619 x 10?30 C m (0.186 D).An approximate structure, based on bond lengths of CC and CH bonds adopted from related molecules, implies that r (Te - C) = 205.5 pm and ? C (5) TeC (2) = 82.53°. 相似文献
Microwave irradiation effectively accelerates cross-coupling metathesis reactions between deactivated olefins. Reactions have been carried out with the phosphine-free Hoveyda-Grubbs catalyst and the "second generation Grubbs' catalyst." While there have been reports that a "microwave effect" is observed in various transformations, the accelerations we observe are due to the efficient and rapid heating and increased pressure in the microwave apparatus. 相似文献
Methane can be converted to ethane and ethylene in a microwave plasma reactor at pressures from 10 to 100 mm Hg. The total methane conversion has a linear correlation with power ? (45 + pressure)/flow and can be as high as 90%. The conversion of methane to ethylene varies from 0 to 11%. It reaches a maximum at a value of Power ? (45 + Pressure)/Flow of 2200 W?mm Hg?s/mL. The energy efficiency of driving this thermodynamically unfavourable reaction is 2%. 相似文献
A method is described which is capable of measuring the dielectric properties of liquids as a continuous function of frequency over the range 10 MHz to 18 GHz; an evaluation is made of its performance over the frequency range up to 4.2 GHz. The method described has substantial advantages in ease of operation and evaluation of results over the conventional “spot” frequency and time-domain spectrometer techniques. 相似文献
Microwave of known amplitude and frequency, irradiating the junction of a low temperature scanning tunneling microscope, was found to induce a dc signal. This rectification current is spatially localized and exhibits chemical sensitivity at the atomic scale. Dependence of the rectification current on the sample bias voltage reveals spin splitting in the electronic state of a single Mn atom and vibrations of single MnCO molecule. These results demonstrate the feasibility of atomic scale nonlinear spectroscopy and the potential for the detection of resonance phenomena excited with a spatially extended electromagnetic wave. 相似文献
The microwave spectra of the four major isotopic species of the unstable molecule selenoformaldehyde have been assigned. The limited number of isotopic variants yields the following structure: r(CSe) = 175.9 pm, ∠(HCH) = 120.4° and r(CH) assumed to be 109 pm. The dipole moment is 1.41 ± 0.01 D. 相似文献