Refractive index generalized complex

The development presented here for the complex impedance, Z = Zr+ jZj, is general and can be applied, for example, to the complex refractive index, the complex viscosity, and the complex permittivity. The derivation for a general transfer function G follows that presented by Nussenzveig. The development for the subsequent analysis in terms of impedance follows the approach presented by Bode. ... 

Refractive Index. The effect of mol wt (1400-4000) on the refractive index (RI) increment of PPG in ben2ene has been measured (167). The RI increments of polyglycols containing aUphatic ether moieties are negative drj/dc (mL/g) = —0.055. A plot of RI vs 1/Af is linear and approaches the value for PO itself (109). The RI, density, and viscosity of PPG—salt complexes, which maybe useful as polymer electrolytes in batteries and fuel cells have been measured (168). The variation of RI with temperature and salt concentration was measured for complexes formed with PPG and some sodium and lithium salts. Generally, the RI decreases with temperature, with the rate of change increasing as the concentration increases. 

Even in modern quality control laboratories you will find a number of traditional methods for the identification of single flavour compounds, for example the estimation of optical rotation, refractive index, density and melting point, since these methods are generally accepted, effective and less time-consuming. Especially for the purpose of fast identification checks of more complex systems, spectroscopic methods, above all infrared (IR) and near-IR spectroscopy, are gaining more and more importance. 

The simple method just described is applicable as it stands only to isotropic solids, that is, to glasses and amorphous solids in general, and to crystals belonging to the cubic system. In all other crystals the refractive index varies with the direction of vibration of the light in the crystal the optical phenomena are more complex, and it is necessary to disentangle them. 

Attention must now be paid to the exponential factor, exp( 2nir (n iij)/A), in Equation 6.5, where (n it) is known as the complex refractive index of a substance. It can be seen that the effect of this factor upon the electromagnetic wave increases with the distance Irl that the light travels in that medium. In the general case of an anisotropic medium, n and are referred to as a specific set of axes, usually chosen to coincide with the optical axes of the medium. For example, the axes of maximum and minimum transmittance are selected for anisotropic absorption. The extinction f for an anisotropic medium is related to the extinction coefficient through Equation 6.9. 

Extensive applications experience has shown that most particulate materials can be analyzed without any consideration of the refractive index. This is generally true because most practical materials have a high index, or are somewhat absorbing. In the exceptional case in which refractive index corrections must be applied, the values of the real and complex indices must be determined carefully. Arbitrary use of index corrections to arbitrarily alter instrument calibration may produce highly erroneous results. Table I serves as a guide to the effects of the refractive index on small particle measurements. 

In this chapter we have reviewed a number of techniques used for optical characterization of organic samples, in particular those concerning the determination of complex optical constants and the dynamics of elementary photoexcitations. It has been stressed that very good optical quality samples are needed in order to obtain reliable estimates of the refractive index. In general, samples with controlled morphology, low defect and impurity concentration, and good optical quality allow more reliable photophysical studies and hence better determination of the intrinsic properties of the material. 

Although values of emittance and absorptance depend in very complex ways on the real and imaginary components of the refractive index and on the geometrical structure of the surface layer, the generalizations that follow are possible. 

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