Dielectric polarization mechanism susceptibility

Molecules for which a temperature-dependent dielectric susceptibility is observed in gas phase are commonly called polar. Polar molecules have microwave spectra with transitions corresponding to AJ= 1 and are deflected by inhomogeneous electric fields. In the conventional approach, these phenomena are attributed to the presence of permanent dipole moments in such molecules. In contrast, the notion of permanent dipole moments (which are zero for spectroscopic states) plays no role at all in the fully quantum-mechanical treatment outlined above. The temperature-dependent component of x arises from the existence of low-lying spectroscopic states for which... 

Recently, Chojnowski89 examined the effect of dielectric constant on the racemization of (l-Naph)PhMeSiCl. A pronounced susceptibility of the reaction to changes in the polarity of the medium was observed. This would be consistent with mechanisms involving intermediates of the form 65 or 49 but not 48. He also examined the rate of transilylation (equation 41), which will involve concurrent racemization of the chiral... 

In Section VI we study in detail two fast short-lived vibration mechanisms b and c, which concern item 2. The dielectric response to the elastic rotational vibrations of hydrogen-bonded (HB) polar molecules and to translational vibrations of charges, formed on these molecules, is revealed in terms of two interrelated Lorentz lines. A proper force constant corresponds to each line. The effect of these constants on the spectra of the complex susceptibility is considered. The dielectric response of the H-bonded molecules to elastic vibrations is shown to arise in the far IR region. Namely, the translational band (T-band) at the frequency v about 200 cm-1 is caused by vibration of charges, while the neighboring V-band at v about 150 cm-1 arises due to elastic rigid-dipole reorientations. In the case of water these bands overlap, and in the case of ice they are resolved due to longer vibration lifetime. 

PAEK can be used as good electrical insulators in a wide range of environments and over a wide range of temperatures. The polar nature of the carbonyl group means that materials such as fluoropolymers have superior dielectric constants and dissipation factors. However, relative to fluoropolymers, PAEK insulation offers lower toxicity in fire situations and more resistant mechanical properties. PAEK can have a relatively low comparative tracking index which measures susceptibility to electrical breakdown on the surface of an insulator. Possibly this reflects the relatively easy degradation of PAEK to carbonaceous char. 

The angle (p denotes a possible phase-lag. For a description of the relation between the polarization and the field, one can again choose, as in the analogous case of the dynamic-mechanical experiment, their complex ratio, known as complex dielectric susceptibility . Rather than the latter, we will use the closely related complex dielectric function e (a ), defined as... 

Let us now look at the dielectric susceptibility in the high temperature phase (T> T c). Both the order parameters q and P are zero in the field-free state, but when an electric field is applied it will induce a polarization and, by virtue of the coupling between P and q, also a nonzero value of q. In the high temperature phase we will thus have a kind of reverse effect brought about by the same coupling mechanism whereas in the low temperature phase a non-zero q induces a finite P, here a non-zero P induces a finite q. 

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