Solvent optical permittivity

If vdielectric permittivity in vacuum will then be equal to 80. This is the so-called static permittivity. The permittivity of the vaccum is 0.855x 10 C m. The static dielectric permittivity near the ion or the surface of the charged electrodes, however, will exhibit smaller values. For instance, in the case of water at the electrode surface is assumed to approach 6. When applying the Marcus theory [8] both static and optical permittivities are used in calculations. These parameters therefore are listed in Table 1. In other calculations and correlations of the rate constants of electrode reactions and the dynamic relaxation properties of the solvents, the relaxation time of the solvents is used (Thble 1). 

According to the Debye model there are three parameters associated with dielectric relaxation in a simple solvent, namely, the static permittivity s, the Debye relaxation time td, and the high-frequency permittivity Eoq. The static permittivity has already been discussed in detail in sections 4.3 and 4.4. In this section attention is especially focused on the Debye relaxation time td and the related quantity, the longitudinal relaxation time Tl. The significance of these parameters for solvents with multiple relaxation processes is considered. The high-frequency permittivity and its relationship to the optical permittivity Eop is also discussed. 

In order to extend the above treatment to the metal solution interface, one must consider the effect of the solvent molecules adsorbed on the metal on the electronic overspill. Because the solvent molecules are polarizable, an induced dipole moment is established in the solvent monolayer, which acts to reduce the extent of overspill. As a result, the dipolar potential due to the metal is reduced by a factor corresponding to the optical permittivity of the monolayer, Sop. Recalling that this dipole potential is designated as one has at the PZC... 

Solvent permittivity — is an index of the ability of a solvent to attenuate the transmission of an electrostatic force. This quantity is also called the -> dielectric constant. -> permittivity decreases with field frequency. Static (related to infinite frequency) and optical op (related to optical frequencies) permittivities are used in numerous models evaluating the solvation of ions in polar solvents under both static and dynamic conditions. Usually the refractive index n is used instead of op (n2 = eop), as these quantities are available for the majority of solvents. The theory of permittivity was first proposed by Debye [i]. Systematic description of further development can be found in the monograph of Frohlich [ii]. Various aspects of application to reactions in polar media and solution properties, as well as tabulated values can be found in Fawcetts textbook [iii]. 

In Eq. (28) e is the charge of the electron, r the radius of the reactant, Avo-gadro s number, and d the reactant-electrode distance. The solvent was considered here as a continuous medium with a fast electronic polarization characterized by the optical dielectric permittivity and a slower oscillatory plus orientational polarization characterized by the static dielectric permittivity... 

As an example, we estimate the resonance enhancement of an intraband optical transition in silicon carbide (SiC) nanociystals. The dielectric function of SiC is well modeled by the expressions (7) with = 6.52, Qt = 793.9 cm" (and the wavelength At = 12.6 pm), = 970.1 cm (Al = 10.3 pm), and y = 4.763 cm. Note that the relaxation parameter y is much less than the optical phonon frequencies, y/Qi = 0.006 and y/ L = 0.005. The solution of the resonance condition (6) results in Q w 902cm and the corresponding resonance wavelength A 11 pm. Here and hereafter, in all onr numerical estimates we accept the permittivity of a host matrix Shost = 2.25, because this value is typical for many solvents, glasses, and polymers. Then, the gain factor G(Q) is estimated to be approximately 3.6 x 10. ... 

Concerning the nature of interaction between a delocalized electron and polar solvents and the dependence of this interaction on the structure and properties of the solvent only a tentative conclusion can be made at present. Vg does not show correlation either with the dimensions of the solvent molecule or with its characteristics such as acceptor and donor numbers, optical and static permittivity, and the molecule s dipole moment. It is obvious that the electron-medium electrostatic interaction alone cannot explain the results obtained. 

For the spectroscopic applications, it would be again instructive to separate the noninertial and inertial components of the electrostatic polarization of the dielectric medium. The first of them corresponds to the electrostatic polarization of the electron charge distribution in the solvent that is supposedly instantaneous as compared to any electronic or conformational transition of the solute. The second component arises from the orientational polarization of the solvent molecules in the electrostatic field of the solute. The noninertial polarization can be described by the optical dielectric permittivity of the solvent that corresponds to the infinite frequency of external electromagnetic field (e Ud) whereas the inertial polarization represents the slow, orientational part of the total dielectric constant of the solvent, s. In order to separate the noninertial polarization, it is helpful to determine the solute charge density as the sum of the respective nuclear and electronic parts... 

In all the previous equations n is the refractive index of the pure solute (i.e. of the aldehyde under study), whereas e and e p, are the static or optical dielectric permittivities of the solvent, which is water in this case. 

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