Dielectric and refractive properties

Potential energy surfaces of weakly bound dimers and trimers are the key quantities needed to compute transition frequencies in the high resolution spectra, (differential and integral) scattering cross sections or rate coefficients describing collisional processes between the molecules, or some thermodynamic properties needed to derive equations of state for condensed phases. However, some other quantities governed by weak intermolecular forces are needed to describe intensities in the spectra or, more generally, infrared and Raman spectra of unbound (collisional complexes) of two molecules, and dielectric and refractive properties of condensed phases. These are the interaction-induced (or collision-induced) dipole moments and polarizabilities. 

Modelling of Dielectric and Refractive Properties of Atomic Gases... 

A is the Hamaker constant for material (1) in medium (3) and H the separation distance between the particles H = R-2a, with R the centre to centre distance). The Hamaker constant depends on the dielectric and refractive properties of the particle material (1) and the dispersant medium (3) and is given by Ref. [26]... 

At present, the major focus of the researchers is on the nanocomposite materials based on the nanoparticles of metals and their compounds stabilized within a polymeric dielectric matrix [1-4]. The dielectric and optical properties of these materials have been demonstrated to be highly dependent on the size, structure, and concentration of the nanopartides, as well as on the type of polymeric matrix [5-8]. These have shown the possibility of the purposeful change of parameters of the nanocomposite materials such as electrical conductivity, complex permittivity, refraction coefficient, and so on. It is believed that these materials would demonstrate low acoustic impedance because they are based on the polymeric matrix [9]. At that, the impedance value should be varied within certain limits by adjusting the parameters of the embedded nanopartides. All of these would allow one to use these materials for low disturbing substrates in various devices based on the waves in thin piezoelectric plates [10]. 

Before closing this section on the three-phase system and the evaluation of film optical properties, a word of caution seems appropriate. Some 15 years ago, when we started to evaluate monolayer optical constants by the three-phase model with sharp boundaries, I was much more optimistic than I am today. The model discussed above (which still seems to be the only one around) has a number of severe drawbacks. For example, the validity of the concept of a macroscopic (continuum) theory for monolayer and submonolayer adsorbates was questioned quite early, although it was hoped that the model would yield an effective film dielectric constant which represents at least average values of the absorptive and refractive properties of the thin film. Application of the continuum theory is especially critical for the direction normal to the... 

The physical properties of saturated fluorocarbons and their analogous hydrocarbons differ in many respects [4 5] Sahirated fluorocarbons have the lowest dielectric constants, surface tensions, and refractive indexes of any liquids at room... 

The dielectric constant and refractive index parameters and different functions of them that describe the reactive field of solvent [45] are insufficient to characterize the solute-solvent interactions. For this reason, some empirical scales of solvent polarity based on either kinetic or spectroscopic measurements have been introduced [46,47]. The solvatochromic classification of solvents is based on spectroscopic measurements. The solvatochromic parameters refer to the properties of a molecule when its nearest neighbors are identical with itself, and they are average values for a number of select solutes and somewhat independent of solute identity. 

According to the mode of parameter correlation, Ej(30) was introduced in the group of parameters that describe the acidity of solvent and partially its polarity, and n in the group of parameters that present the dielectric properties of solvents. Quantitative relations between different parameters of polarity, such as correlation between the n scale or and the dielectric constant and refractive index of... 

Quantitative determination of solvent polarity is difficult, and quantitative methods rely on physical properties such as dielectric constant, dipole moment and refractive index. It is not possible to determine the solvent polarity by measuring an individual solvent property, due to the complexity of solute-solvent interactions, and for this reason empirical scales of solvent polarity based on chemical... 

Thus, we see the initial connection between optical properties and the electrical and magnetic properties from the two previous sections. Substimtion of Eqs. (6.78) and (6.79) into (6.77) shows that the refractive index can be expressed in terms of the relative electric permittivity (dielectric constant), (cf. Table 6.5), and relative magnetic permeability of the medium, (1 - - x) [cf. Eq. (6.63)], where x is the magnetic susceptibility ... 

The physical properties of solvents greatly influence the choice of solvent for a particular application. The solvent should be liquid under the temperature and pressure conditions at which it is employed. Its thermodynamic properties, such as the density and vapor pressure, temperature and pressure coefficients, as well as the heat capacity and surface tension, and transport properties, such as viscosity, diffusion coefficient, and thermal conductivity, also need to be considered. Electrical, optical, and magnetic properties, such as the dipole moment, dielectric constant, refractive index, magnetic susceptibility, and electrical conductance are relevant, too. Furthermore, molecular... 

Physical properties of the solvent are used to describe polarity scales. These include both bulk properties, such as dielectric constant (relative permittivity), refractive index, latent heat of fusion, and vaporization, and molecular properties, such as dipole moment. A second set of polarity assessments has used measures of the chemical interactions between solvents and convenient reference solutes (see table 3.2). Polarity is a subjective phenomenon. (To a synthetic organic chemist, dichloromethane may be a polar solvent, whereas to an inorganic chemist, who is used to water, liquid ammonia, and concentrated sulfuric acid, dichloromethane has low polarity.)... 

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

IR spectra measurements as well as variation of the film thickness, shrinkage, and refractive index demonstrated substantial differences in the mechanisms of thermal decomposition of films prepared from the exclusively metal alkoxide precursor and from the metal alkoxides modified by 2-ethylhexanoic acid. These differences affect the evolution of film microstructure and thus determine the different dielectric properties of the obtained films. The dielectric permittivity of the films prepared from metal alkoxide solutions was relatively low (about 100) and showed weak dependence ofthe bias field. This fact may be explained by the early formation of metal-oxide network (mostly in the... 

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]. 

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