Microwave calculated

Because of point 2, rotational microwave and millimetre wave spectroscopy are powerllil techniques for determining dipole moments. However, the direction of the dipole moment cannot be determined. In the case of 0=C=S, for which /r = 0.715 21 0.000 20 D [(2.3857 0.0007) x 10 ° C m], a simple electronegativity argument leads to the correct conclusion - that the oxygen end of the molecule is the negative end of the dipole. However, in CO, the value of 0.112 D (3.74 x 10 C m) is so small that only accurate electronic stmcture calculations can be relied upon to conclude correctly that the carbon end is the negative one. 

The apphcation of microwave power to gaseous plasmas is also of interest (see Plasma technology). The basic microwave engineering procedure is first to calculate the microwave fields internal to the plasma and then calculate the internal power absorption given the externally appHed fields. The constitutive dielectric parameters are useful in such calculations. In the absence of d-c magnetic fields, the dielectric permittivity, S, of a plasma is given by equation 10 ... 

Various data sources (44) on plasma parameters can be used to calculate conditions for plasma excitation and resulting properties for microwave coupling. Interactions ia a d-c magnetic field are more compHcated and offer a rich array of means for microwave power transfer (45). The Hterature offers many data sources for dielectric or magnetic permittivities or permeabiHty of materials (30,31,46). Because these properties vary considerably with frequency and temperature, available experimental data are iasufficient to satisfy all proposed appHcations. In these cases, available theories can be appHed or the dielectric parameters can be determined experimentally (47). 

The alternative of lower cost r-f systems, ie, induction and r-f heating systems at 40 MH2 and below, should be considered (96) (see also Furnaces, electric). More extensive discussions of the economic aspects of microwave systems and payback calculations are available (97,98). 

A large number of arsenin derivatives have also been studied. The potential aromaticity of this ring system has aroused considerable interest and has been investigated with the aid of nmr, uv, photoelectron, and microwave spectroscopy as well as by ab initio molecular orbital calculations (119). Arsenin does possess aromatic character. 

IP, isolated pure MI, matrix isolated GP, data from pure gas phase material CE, chemical evidence for existence TH, theoretical calculation XR, X-ray structure MW, microwave structure UV ultraviolet spectrum. 

Furazano[3,4-/]quinoxaline, 7,8-diphenyl-synthesis, 6, 412 Furazanothiophene synthesis, 6, 417 Furazans, 6, 393-426 biological activity, 6, 425 bond angles, 6, 396 bond lengths, 6, 396 coordination compounds, 6, 403 diamagnetic susceptibilities, 6, 395 dipole moments, 6, 395, 400 heats of combustion, 6, 400 heterocyclic ring reactions, 6, 400-403 IR spectra, 6, 398 isoxazoles from, 6, 81 mass spectra, 6, 399 microwave spectroscopy, 6, 395, 396 MO calculations, 6, 395 monosubstituted... 

Conformations A and B are of the eclipsed type, whereas C and D are bisected. It has been determined by microwave spectroscopy that the eclipsed conformations are more stable than the bisected ones and that B is about 0.15 kcal more stable than A. MO calculations at the 6-31G level have found relative energies of 0.00, —0.25, 1.75, and 1.74kcal/mol, respectively, for A-D. ... 

Molecular electric quadrupole moments are more elusive animals, and they are not particularly easy to determine experimentally. Prior to 1970, the only direct routes to these quantities were from the Kerr and Cotton-Mouton effects. They can now be obtained from microwave Zeeman spectroscopy, to fair accuracy. It is fair to say that direct calculation offers a faster and more reliable route to this property than experiment. 

The determination of molecular structure by microwave spectroscopy (Section VII,A), the measurement of acid-base equilibria by ICR (Section VII,F), and theoretical calculations, especially accurate for the gas phase, are the main novelties of this section. 

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