Electric fields, stray

The electronic transitions which produce spectra in the visible and ultraviolet are accompanied by vibrational and rotational transitions. In the condensed state, however, rotation is hindered by solvent molecules, and stray electrical fields affect the vibrational frequencies. For these reasons, electronic bands are very broad. An electronic band is characterised by the wave length and moleculai extinction coefficient at the position of maximum intensity (Xma,. and emai.). 

A second important need for some guidance system lies in stray electric fields. Clearly, a sufficiently large potential arranged transversely to an ion beam can serve to deflect ions away from the intended direction. Such stray fields can be produced easily by sharp edges or points on the inside of a mass spectrometer and even more so in an ion guide itself. Considerable care is needed in the construction and design of mass spectrometers to reduce these effects to a minimum. 

Greater deviations which are occasionally observed between two reference electrodes in a medium are mostly due to stray electric fields or colloid chemical dielectric polarization effects of solid constituents of the medium (e.g., sand [3]) (see Section 3.3.1). Major changes in composition (e.g., in soils) do not lead to noticeable differences of diffusion potentials with reference electrodes in concentrated salt solutions. On the other hand, with simple metal electrodes which are sometimes used as probes for potential controlled rectifiers, certain changes are to be expected through the medium. In these cases the concern is not with reference electrodes, in principle, but metals that have a rest potential which is as constant as possible in the medium concerned. This is usually more constant the more active the metal is, which is the case, for example, for zinc but not stainless steel. 

Static electricity hazards and nuisances are typified by the generation of large potentials (0.1-100 kV) by small charging currents (0.01-100 pA) flowing in high resistance circuits (10 -10 Q). This in part differentiates static electricity from other electrical phenomena. For example, stray currents in low resistance circuits are typically of the order 1 A for potential differences of the order 1 volt (A-4-1.3). The electric field at any point in relation to a conductor is proportional to its potential, while magnetic field is proportional to... 

The precautions generally applicable to the preparation, exposure, cleaning and assessment of metal test specimens in tests in other environments will also apply in the case of field tests in the soil, but there will be additional precautions because of the nature of this environment. Whereas in the case of aqueous, particularly sea-water, and atmospheric environments the physical and chemical characteristics will be reasonably constant over distances covering individual test sites, this will not necessarily be the case in soils, which will almost inevitably be of a less homogeneous nature. The principal factors responsible for the corrosive nature of soils are the presence of bacteria, the chemistry (pH and salt content), the redox potential, electrical resistance, stray currents and the formation of concentration cells. Several of these factors are interrelated. 

H. J. Neusser For a selected intermediate J K> state we observe a couple of Rydberg series for example, for J K, = li we can identify two series under minimum residual field conditions. When we apply a stationary electric field of 300 mV/cm, additional series appear that are coupled by the electric field. All series have different limits representing different rotational states of the benzene cation. At present we cannot say whether the coupling observed under minimum residual field conditions is induced by the small stray field or by field-free intramolecular coupling. 

Unfortunately it is not going to be easy to test experimentally or even to simulate on the computer. The reason is the extreme sensitivity of states of high n to external perturbations. In the laboratory, stray electrical fields, which cannot be completely avoided (or black-body radiation) will cause ionization of these states. Even on the computer, numerical roundoff errors will act as external noise. 

In order to test the measurements of the 2S — 8S and 2S — 8D transitions, the frequencies of the 2S — 12D intervals have also been measured in Paris [49]. This transition yields complementary information, because the 12D levels are very sensitive to stray electric fields (the quadratic Stark shift varies as n7), and thus such a measurement provides a stringent test of Stark corrections to the Rydberg levels. The frequency difference between the 2S — Y2D transitions (A 750 nm, u 399.5 THz) and the LD/Rb standard laser is about 14.2 THz, i.e. half of the frequency of the CO2/OSO4 standard. This frequency difference is bisected with an optical divider [56] (see Fig. 5). The frequency chain (see Fig. 11) is split between the LPTF and the LKB the two optical fibers are used to transfer the CO2/OSO4 standard from the LPTF to the LKB, where the hydrogen transitions are observed. This chain includes an auxiliary source at 809 nm (u 370.5 THz) such that the laser frequencies satisfy the equations ... 

A possible explanation of the production of the (2S-2P) superposition is based on the assumption that there are electric charges on the metal surface creating the electric field, that mixes 25 and 2P states. To refute such arguments a series of experiments had been executed in conditions when the influence of any stray fields inside the interferometer was completely excluded [2]. It appeared however, that all taken measures were unable to annihilate the observed long-distant interaction effect. At last we had to conclude that we were dealing with some kind of previously unknown long-range interaction. Further experiments confirmed such an assumption. 

Great care has been taken in the experimental set-up to avoid any stray field. In order to evaluate the effect of residual electric fields we have... 

Be alert to possible external disturbances—such as high humidity, mechanical vibrations, stray electric fields, voltage fluctuations, unusual local heating—and internal misbehaviors—such as vacuum leaks, nonhnear meter readings, hysteresis. Some of these may cause equipment failure or result in noisy, erratic readings. Some can introduce subtler troubles in the form of systematic errors, where the data look fine but are not. See Chapter II for a detailed discussion of errors. 

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