Linear electric field

Sc, carbon chemical shift, referred to tetramethylsilane (8 = 0) (cf. Sect. I) SCS, substituent-induced chemical shift, or substituent effect difference between S s of a given carbon atom in a monosubstituted and the respective unsubstituted parent molecule (cf. Sect. Ill) NAE, nonadditivity effect nonadditivity of individual SCSs in disubstituted molecules (cf. Sect. IV) ICS, intramolecular-interaction chemical shift = NAE (cf. Sect. IV) A, polarization effect difference in S s of sp2 carbon atoms in a double bond (cf. Sect. IV-C) LEF, linear electric field (cf. Sect. II-B-3) SEF, square electric field (cf. Sect. II-B-3). 

The first term in eq. [8] is the linear-electric-field (LEF) effect (74-77), which may be interpreted as a charge separation AQC(i)Y along the C(i)-Y bond (76) ... 

If a molecule is subjected to a linear electric field E that is fluctuating such that... 

Assume now that the ejected ions are distributed isotropically on the surface of the expanding sphere, and that linear electric fields along the z axis project the sphere perfectly onto the PSD. The 3-D bubble of ions will flatten to a disk on the detector with the highest ion intensity lying at the outer edge of the disk, forming a circle of radius... 

ESR-active clusters will be oxidized 3Fe, oxidized HiPIP, reduced 2Fe and reduced 4Fe (Fd). Further distinction may be made by consideration of the dependence on magnetic fields of the shift in g value induced by an externally applied electric field (linear electric field effect). This effect is similar for 3Fe and 4Fe ferredoxins, but is considerably different for both 2Fe and HiPIP clusters, which also differ from each other. Thus, all four classes of iron-sulfur protein (2Fe, 3Fe, Fd and HiPIP) may be distinguished by a combination of ESR and LEFE properties.814 ... 

For the chemist, there is no doubt whatsoever that the softness of the central atoms do not follow the a values, though this is valid for the halides. Thus, Cs(I) is more polarizable than Ag(I), Ba(II) more than Cd(II) and La(III) more than In(III) in disagreement with Pearson s classification. Said in other words, the chemical bonding involves far stronger perturbations than the linear electric fields inducing the a-polarizability. 

Kama recently reported an ab initio study of linear electric field effects on the g-tensor and on the hyperfine splitting constant (the Bloembergen effect) of the silyl radical ( SiH3)13. TDUHF calculations predict an increase in hyperfine splitting in "SiH3 due to the Bloembergen effect, predictions which have yet to be verified experimentally. 

Mims, W. B. The Linear Electric Field Effect in Paramagnetic Resonance, Oxford, Clarendon 1976... 

An alternate and convenient method of expressing the work required to push the negative test charge toward the interface is given by the electric potential at each point in the semiconductor. Electrostatics states that the electric potential is equal to the negative integral of the electric field over the path of interest. Thus, integrating the linear electric field (eqnation 1) from the bulk of the semiconductor toward the semiconductor/metal interface yields a quadratic expression for the electric potential in the semiconductor phase ... 

This feature has frequently been introduced in various ad hoc empirical fashions in dielectric discussions. One analytically explicit form was used by Piekara (1939) to account for the non-linear electric field effects, e.g. in liquid nitrobenzene. The importance of these effects is in part precisely because they allow a sensibly direct appraisal of dipole inter-correlations (see Chapter 7). 

It is to Piekara and his collaborators that we owe almost all the currently available significant data on non-linear electric field effects in condensed molecular systems, including at least three different forms of molecular response. See Ann. Reports (,A), 1970, 67, 87— 96. (Note by Senior Reporter.)... 

Obviously, in strongly dipolar substances, the purely dipolar constant will be the predominant one and consequently this treatment of gas theory results in a negative saturation effect. Numerical values of molar non-linear electric field constants (259) are listed in Table 15 for some of the more important non-dipolar as well as dipolar molecules. 

The Onsager Model in the Non-linear Electric Field Effect. The non-linear dectric field theory of Debye disagrees with most of the measurements of Ac in liquids and thdr solutions. To Van Vleck is due the atten t to reduce the discrepandes by applying Onsager s local electric field model in the treatment of the field effect. Aiming at simplidty, he considered only the influence of reorientation of ri d (not polarizable) electric dipoles p,... 

A variety of spectroscopic and physical techniques have been used to investigate the nature of these redox centers. EPR, Fe Mossbauer spectroscopy, and Mo and Fe X-ray absorption spectroscopy Mo, Fe, and H electron-nuclear double resonance (ENDOR) linear electric field effect and magnetic circular dichroism (MCD) have provided information about the environment of the Mo and Fe nuclei and their interaction with the unpaired spin of electrons in paramagnetic species of the MoFe proteins. 

To obtain the spin-Hall current, it is necessary to analyze the hole distribution function. Within the linear response regime, we find that the linear electric field part of the helicity-basis distribution function, j(p), can be written as a sum of two terms,... 

Note Ring-current (anisotropy) effects 60-85% (orientation dependent). Linear electric field effects 15-40% (orientation dependent) complexation-induced shifts in ppm. 

The two derivatives Ag Cu and CU2CU2SOD [the latter obtained through semireduction of Cu Cu SOD] show quite similar visible absorption and EPR spectra 244, 252). The spectra are characteristic of Cu(II) in the zinc site without interference from paramagnetic ions in the copper site. The h3q)erfine coupling constant of 105 X 10 cm" is typical of copper(II) tetrahedral complexes 244, 252). Experiments based on linear electric field effect (LEFE) in pulsed EPR also support the conclusion that Cu(II) in the zinc site retains the pseudotetrahe-dral coordination geometry. Furthermore, ENDOR and ESEEM experiments on Ag 2Cu2 SOD pointed out that Cu(II) forms inequivalent bonds to the three coordinated imidazoles 289). 

High concentrations of ions with small radii of hydration such as H3O+, K+, and OH should be avoided. These small ions are rapidly transported within the linear electric field of the capillary, resulting in high electric currents. For this reason, ions with lower mobility such as Li+ and CH3COO should be substituted wherever possible. ... 

Several spectroscopic techniques have been used to study nitrogenase proteins both in the isolated forms and during enzymatic activity. These include electron paramagnetic resonance (epr) spectroscopy, Mossbauer spectroscopy, uv-visible spectrophotometry, circular dichroism. X-ray absorption edge and fine structure spectroscopy (EXAFS), and linear electric field effects (LEFE). 

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