Static dielectric susceptibility

The e-mv couplings play an important role in superconductivity in organic materials, which contributes to static dielectric susceptibility. It is necessary to notice that not only totally symmetric modes couple with the electrons some out-of-plane molecular modes and intermolecular modes can also couple with the electron excitations. 

First, consider a very dilute gas of molecules [16]. The conventional theory of the static dielectric susceptibility % of such a gas invokes the notion of polarizable molecules with permanent dipole moments that are partially aligned by the external electric field . Standard techniques of statistical thermodynamics produce the Langevin-Debye formula for x Per molecule that reads... 

It is not clear, whether the experimentally observed random local freezing of the deuterons in the O-D—O bonds in deuteron glasses corresponds to a true thermodynamic phase transition or whether one deals with a dynamic phenomenon which only seems static because of the finite observation time of the experimental techniques. The recently observed42 splitting between the field-cooled and zero-field dielectric susceptibilities below an instability temperature Tf seems to speak for the occurrence of an Almeida-Thouless-like thermodynamic phase transition in deuteron glasses. It is well known that ID NMR and EPR allow a direct measurement of the Edwards-Anderson order parameter qEA only on time scales of 10 3-10 8 s and 2D exchange NMR possibly seems to be a better technique for such slow motions. 

N is the number density, 33 is a component of the molecular nonlinear optical susceptibility, is the static dipole moment, Ep is the poling field, e is the static dielectric constant, n is the index of refraction, and where the f s are local field factors at the appropriate frequencies (r - + 2)/3). 

FIGURE 7.13. (a) Static hysteresis of macroscopic polarization P E) and (b) dielectric susceptibility x E) = dPjdE for an FLC cell. A14 is defined as the hysteresis width. 

The dielectric constant of the vaccum c(j is included in the susceptibility definitions as SI units are used throughout this work. The analogous definition can be applied to the microscopic polarization p of a molecule with the molecular dipole moment jli and the polarizabilities a,/3, and y instead of the static polarization P (0) and the susceptibilities y-P. 

Figure 49. Susceptibility spectra for propylene carbonate (Tg — 160 K) as measured by depolarized light scattering (top, data from Ref. 372) and dielectric spectroscopy (bottom, data from Ref. 9), each normalized by a temperature-independent static susceptibility. The full lines are fits from solutions of a two-component schematic MCT model. The dashed fines indicate a white noise spectrum. The dash—dotted line in the upper panel exhibits the asymptote of the critical spectrum. The dotted line shows the solution of the model at T — Tc with hopping terms being neglected. (From Ref. 380.)...

Many of the different susceptibilities in (18)-(21) correspond to important experiments in linear and non-linear optics. The argument in parentheses again describes the kind of interacting waves. TWo waves interact in a first-order process as described above in (9), three waves in a second-order process, and four in a third-order process. x ° describes a possible zeroth-order (permanent) polarization of the medium t- (0 0) is the first-order static susceptibility which is related to the relative permittivity (dielectric constant) at zero frequency, e,.(0), by (22). 

The very thin dielectric layer that separates the gate from the charmel in a FET is very susceptible to breakdown from static charge before the chip is installed in the device. For this reason such chips are shipped in conductive static-proof packages and extreme care in handling such components must be exercised. 

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