Crystal optical properties various materials

Ordered (and partially ordered) arrays of metal sites and complexes enable the cooperation of their special electronic, magnetic and optical properties. Such materials have long been sought for their expected physical properties and applications in optics, electrooptics, superconductivity and sensors. The ordering can be by various mechanisms, such as adsorption on surfaces, intercalation into layered structures, formation of mesomorphic structures and liquid crystals, and adoption of specific crystal-packing motifs, all of which are supramolecular phenomena. Organic liquid crystals and their applications are now commonplace, and in recent years the incorporation of metal atoms into mesogenic molecules has demonstrated the occurrence of similar metallo-mesophases [20]. 

Crystal elastic constants, 12-33 to 38 Crystal ionic radii, 12-11 to 12 Crystal lattice energy, 12-19 to 31,12-32 Crystal optical properties elements, 12-121 to 145 inorganic compounds, 10-246 to 249 minerals, 4-149 to 155 various materials, 12-146 to 164 Crystal structure... 

Multi-photon-induced modification of optical properties of materials including refractive index, absorbance, polarization and fluorescence appearance or wavelength shifting could be utihzed for 3D optical memory in various media, including polymers, inorganic crystals, or glasses. 

Actual crystal planes tend to be incomplete and imperfect in many ways. Nonequilibrium surface stresses may be relieved by surface imperfections such as overgrowths, incomplete planes, steps, and dislocations (see below) as illustrated in Fig. VII-5 [98, 99]. The distribution of such features depends on the past history of the material, including the presence of adsorbing impurities [100]. Finally, for sufficiently small crystals (1-10 nm in dimension), quantum-mechanical effects may alter various physical (e.g., optical) properties [101]. 

Many substances can rotate the plane of polarization of a ray of plane polarized light. These substances are said to be optically active. The first detailed analysis of this phenomenon was made by Biot, who found not only the rotation of the plane of polarization by various materials (rotatory polarization) but also the variation of the rotation with wavelength (rotatory dispersion). This work was followed up by Pasteur, Biot s student, who separated an optically inactive crystalline material (sodium ammonium tartrate) into two species which were of different crystalline form and were separately optically active. These two species rotated the plane of polarized light equally but in opposite directions and Pasteur recognized that the only difference between them was that the crystal form of one was the mirror image of the other. We know to-day, in molecular terms, that the one necessary and sufficient condition for a substance to exhibit optical activity is that its molecular structure be such that it cannot be superimposed on its image obtained by reflection in a mirror. When this condition is satisfied the molecule exists in two forms, showing equal but opposite optical properties and the two forms are called enantiomers. 

Recently in the field of physics of semiconductors and materials science a great attention has been paid to formation and optical properties of semiconductor nanocrystals (quantum dots, QDs) dispersed in inorganic matrixes. An interest to glassy materials with QDs is associated with their unique physical properties and possibility to create elements of optoelectronic devices. Phase separation processes followed by crystallization are the basic in production of such materials. They result in formation of semiconductor nanocrystals stabilized within a glass matrix. The materials are advanced for various applications because of optical and thermal stability and possibility to control optical features through the technology of glass preparation and post-synthesis thermal treatment. 

This reaction, called a four-center photopolymerization, is a typical example of topochemical reactions used to prepare polymer crystals.5 The changes in higher-order structure during the reaction are shown in Table 2.5 . Various polydiacetylene crystals have also been prepared by solid-state photopolymerization of diacetylene monomer crystals, such as 1,6-dicarbazoyl-2,4-hexadiene. These syntheses have attracted considerable interest, since they can lead to organic materials of high conductivity or of nonlinear optical properties. 

Tapes and ribbons have been of interest in crystal engineering due to various applications in material sciences. Stabilization of the translation of molecules through intermolecular forces in a solid can generate polarity, which is a necessary condition for a number of physical properties. For example, small-molecule nitroaniline compounds show preference for a motif that involves one amino proton associating with both oxygens of a nitro group, leading to the formation of a tape structure (Fig. 3). In particular,p-nitroaniline (1) has been studied for its non-linear optical properties [21]. 

The optical properties of rare-earth doped yttrium oxide and other rare-earth oxides have been studied extensively for several years, since the oxides are excellent laser host materials. Laser action of EurYjOs has been observed at 0.6113/xm (Chang, 1963) Nd Y203 has also been studied as a laser crystal (Hoskins and Softer, 1964 Holloway et al., 1%6). Recently, a Nd tYjOs crystal was used as a room-temperature frequency converter laser output was observed at 1.07 /Lim and at 1.31 /i,m when the crystal was pumped by a Kr c.w. laser (Stone and Burrus, 1978). The possibility of an X-ray pumped laser using various rare-earth ions in Y2O3 has also been discussed (Ratinen, 1971). Other applications of Y2O3 such as thermionic emission (Kul varskaya, 1976) and electroluminescence (Tanaka et al., 1976) have also been described. 

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