Sapphire 706 INDEX

In addition, combining the microscope with the use of a pulsed laser light source provides temporal information on these systems in a small domain. The dispersion of refractive index, however, strongly affects the temporal resolution in the measurements of dynamics under the microscope and typical resolution stays around 100 fs when a Ti Sapphire laser is used as an excitation source. 

A different system has been introduced by Index Instruments [2]. This modular analysis system (MAS) provides the analysis of up to four different parameters refractive index, density, colour and optical rotation. A wide range of viscosities can be handled. The analysis, wash and drying times can be selected by computer control so that crosscontamination can be reduced to undetectable levels. Samples are only in contact with inert materials such as glass, synthetic sapphire, PTFE and 316 stainless steel. 

Attenuated total internal reflection (ATR) probes offer several advantages over other probe types. ATR is a phenomenon that relies on a difference in the index of refraction of a crystal and that of the solution with which it is in contact to prevent light from escaping the crystal. Only the evanescent wave of the light interacts with the solution layer at the crystal face. The result is an optical pathlength of only a few microns. Typical designs make use of faceted crystals or hemispheres (see Figure 6.1). The most common ATR material in the UV-vis is sapphire. In rare cases, fused silica may be used. ATR allows spectra to be taken of neat samples with optical density (OD) of 500-1000... 

The gray values in Fig. 10 and in Fig. 11 are 2D projections into the. rv-plane. Because of the phase contrast technique, they are approximately linear functions of the integral over the refractive index along the z-direction. The temperature and concentration distribution and, hence, also the refractive index are fully 3D objects. The high thermal conductivity of the sapphire windows enforces a constant temperature boundary condition at the top and bottom windows. 

Spinel is a colorless magnesium aluminate (MgAl204) of cubic structure. It is hard and durable, but, like white sapphire, it is not a good diamond substitute because it has a low refractive index and lacks brilliance. However, it is readily doped to produce other gems of various colors. Artificial ruby, for example, is often natural red spinel, and most synthetic blue sapphires on the market are actually blue spinel. 

In practice, a convenient range of solid crystalline materials, which can be polished to optical flatness over manageable areas, exists and includes silicon, quartz, and sapphire. The equivalent transmission through a block of amorphous quartz or silicon is 10—15%. This has so far precluded them from use, and limited the application to crystalline substrates. In aqueous solution, the most commonly use contrasts are D20, H20, and water (H20/D20 mixture) index matched to the solid phase. In D20, the refractive index (or scattering length density) difference between that and the solid phase is significantly different for silicon, quartz, and sapphire (see Table 1). 

From silicon to sapphire, the difference in scattering length density or refractive index compared with D20 is progressively smaller, which makes the region of total reflection more difficult to access, but enhances the sensitivity of... 

Table 21 Refractive Index of sapphire at 25°C in the spectral range where k < 10-6, from [49, 50]...

Table 24 Refractive index, n, and absorption index, k, of the ordinary ray for sapphire in the infrared spectral range, at 25°C, from [49] ...

Sapphire was selected as an internal reflection element with a high value of refractive index (n. = 1.81 at 313 nm). It is transparent down to 200 nm, mechanically hard, chemically stable, and has a small birefringence. The dimension of the used plate... 

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