Electrical potential scattering

Lately, some reports appeared about a new potential measurement technique with application of electric field scattering (frequency 1 MHz) [84,85]. This method is very interesting, for the possibility of the measurements in the condensed suspensions. It will allow to determine the stability of the suspension and developed investigations of the edl structure. To obtain precise values of the potential by this method, the knowledge of particle size distribution of the suspension is necessary. Previously used electrophoretic techniques, enabled the measurements to be taken only in the dilute solutions, which do not characterize the systems properly. 

Electrophoretic light scattering (ELS) is commonly used to measure v. The electrophoretic mobility /r can be calculated from v and the known value of E according to Eq. (I). Theoretical models [ I.7-I0] that describe colloidal electrostatics and hydrodynamics can then be used to relate the measured values of n to particle electrical characteristics including surface charge density and surface electric potential. Because /r depends on the surface electrostatic properties but not particle bulk properties, ELS can characterize surface electrostatic properties exclusively for a wide range of colloidal materials. 

FIGURE 3.7. The time course of electric potential. Time 0 indicates the onset of the first oscillation, (b) The simultaneous measurement of the time course of interfacial tension. The value at the onset of each oscillation fluctuated due to the macroscopic wave-linked interfacial movements and the subsequent fluctuation of the scattered light. A few tens of seconds after the onset of oscillation, we could measure the interfacial tension correctly again. 

The positions of the diffraction spots give us the unit cell information. The intensities of these spots are dependent on the positions of atoms, i.e. the crystal structure. Electrons are scattered by the electrical potential in a specimen, < )(r) and the scattering factor,, may be written as ... 

X-ray diffracLion, Lhe X-rays are scattered by the electron clouds around individual atoms. Since the atoms and molecules of the liquid sample are not fixed in space, the information resulting from the diffraction experiment must be interpreted in terms of statistical averages. The neutrons used in a neutron diffraction experiment are scattered by the nuclei of the atoms in the liquid sample so that the scattering pattern is quite different from that for X-rays. In electron diffraction, the electrical potential, which depends on the spatial configuration of the nuclei and electronic density distribution, determines the diffraction pattern. Early experiments involved simple monoatomic liquids such as the inert gases and liquid metals. However, many molecular liquids have also been studied, including polar liquids such as water, the alcohols, and amides [5]. In this section, attention is focused on two of these techniques, namely. X-ray and neutron diffraction. 

Adsorption of radiation Scattering of radiation Refraction of radiation Diffraction of radiation Rotation of radiation Electrical potential Electrical current Electrical resistance Mass to charge ratio Rate of reaction Thermal properties Mass Volume... 

An electric potential of a substance is probed by charge particles emitted, for example, by an electronic gun or an accelerator. The electron beam is scattered by the electric potential of positive nuclei and negative electrons and the maximum positive potential corresponds to the center of an atom. The electrons in the beam have the de Broglie wavelength dependent on their velocity v, i. e. on the accelerating voltage V, namely, eV = = W... 

There are several differential equations that are related to Laplace s equation, e.g. the Poisson equation for the distribution of electric potential in the presence of electric charges, the wave equation for the propagation of a disturbance or the Helmholtz differential equation for the time-invariant distribution of harmonic fields. The latter is of particular relevance for scattering phenomena it has the form ... 

W. Richter, Resonant Raman Scattering in Semiconductors Electric Susceptibility. Light Scattering. Experimental Method.s. One-Phonon Deformation Potential Scattering. Infrared Active LO Phonons. Multiphonon Scattering. Conclusions. List of Symbols. References. Subject Index. 

If the incident wave is an X-ray beam, the interaction with the crystal (i.e., what the incident beam sees ) is the electronic density p(r) in the atom volume (p(r) is nil outside). If the incident wave is an electron beam, the interaction happens both with electrons and the nucleus (i.e., the wave sees the electrical potential of the atom). The atomic scattering factor/ is proportional to (Z - fx.Ray)-... 

Correspondingly, the scattering factorsand/ are, respectively, the FT of the electronic density p(r) in the atom and the FT of the atom electrical potential V. ... 

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