Refractive indices, defined

In these expressions x is the size parameter and m is the relative refractive index, defined by... 

If monochromatic light moves from a vacuum into a non-absorbing medium with a refractive index n, the frequency v remains the same but the velocity and wavelength decrease to dn and kin. Equation (3.14) indicates that the refractive index, defined as c/m, can be equated with... 

For the calculations based on Mie theory the optical properties such as refraction and absorption of the dispersed and continuous phase are included in the form of a complex refractive index defined as follows ... 

If the scattering particles are in a dielectric solvent medium with solvent refractive index Uq, we can define the excess... 

The geometry of Fig. 10.3 leads to a result known as Snell s law, which relates the refractive index of the medium to the angles formed by two wave fronts with the interface. Defining 6q and 6, respectively, as the angles between the phase boundary and the wave front under vacuum and in the medium of refractive index n, show that Snell s law requires n = sin Oo/sind. 

Other terms relating to physical properties include viscosity refractive index pour point, ie, the lowest temperature at which the oil flows flash point, ie, the temperature at which the oil ignites and aniline point, ie, the minimum temperature at which equal volumes of oil and aniline are completely miscible. These are determined under defined conditions estabHshed by ASTM. 

Capillary gc/ms, hplc, nmr, ir, and uv are all analytical methods used by the terpene chemist with a good Hbrary of reference spectra, capillary gc/ms is probably the most important method used in dealing with the more volatile terpenes used in the davor and fragrance industry (see Flavors and spices). The physical properties of density, refractive index, boiling point, melting point of derivatives, and specific rotation are used less frequendy but are important in defining product specifications. 

In Raman spectroscopy the intensity of scattered radiation depends not only on the polarizability and concentration of the analyte molecules, but also on the optical properties of the sample and the adjustment of the instrument. Absolute Raman intensities are not, therefore, inherently a very accurate measure of concentration. These intensities are, of course, useful for quantification under well-defined experimental conditions and for well characterized samples otherwise relative intensities should be used instead. Raman bands of the major component, the solvent, or another component of known concentration can be used as internal standards. For isotropic phases, intensity ratios of Raman bands of the analyte and the reference compound depend linearly on the concentration ratio over a wide concentration range and are, therefore, very well-suited for quantification. Changes of temperature and the refractive index of the sample can, however, influence Raman intensities, and the band positions can be shifted by different solvation at higher concentrations or... 

Phase composition changes as a function of temperature are similar to these that were observed for the lithium-containing system (see Fig. 21), except that individual stable ammonium-cobalt-oxyfluoroniobate occurs prior to the formation of CoNbOF5 (Fig.21, curve 4). It is assumed that the composition of this intermediate phase, formed at 330-350°C, is (NH CoNbOFy [129]. Complete removal of ammonium occurs at about 400°C (Fig. 21, curve 5) and leads to the formation of CoNbOFs. The compound is defined as practically isotropic rose-colored ciystals with a refractive index of N = 1.500. The... 

In this Section we want to present one of the fingerprints of noble-metal cluster formation, that is the development of a well-defined absorption band in the visible or near UV spectrum which is called the surface plasma resonance (SPR) absorption. SPR is typical of s-type metals like noble and alkali metals and it is due to a collective excitation of the delocalized conduction electrons confined within the cluster volume [15]. The theory developed by G. Mie in 1908 [22], for spherical non-interacting nanoparticles of radius R embedded in a non-absorbing medium with dielectric constant s i (i.e. with a refractive index n = Sm ) gives the extinction cross-section a(o),R) in the dipolar approximation as ... 

The transition between crystalline and amorphous polymers is characterized by the so-called glass transition temperature, Tg. This important quantity is defined as the temperature above which the polymer chains have acquired sufficient thermal energy for rotational or torsional oscillations to occur about the majority of bonds in the chain. Below 7"g, the polymer chain has a more or less fixed conformation. On heating through the temperature Tg, there is an abrupt change of the coefficient of thermal expansion (or), compressibility, specific heat, diffusion coefficient, solubility of gases, refractive index, and many other properties including the chemical reactivity. 

From Eq. (3) derive the relations for the real and imaginary parts of the refractive index as Auctions of the permittivity and the electrical conductivity of a given medium. Note drat both n and k are defined as real quantities. 

If measurements are made in thin oxide films (of thickness less than 5 nm), at highly polished Al, within a small acceptance angle (a < 5°), well-defined additional maxima and minima in excitation (PL) and emission (PL and EL) spectra appear.322 This structure has been explained as a result of interference between monochromatic electromagnetic waves passing directly through the oxide film and EM waves reflected from the Al surface. In a series of papers,318-320 this effect has been explored as a means for precise determination of anodic oxide film thickness (or growth rate), refractive index, porosity, mean range of electron avalanches, transport numbers, etc. 

---