Subject optical properties

Dienes and polyenes have been a subject of great interest due to their important role in biology, materials science and organic synthesis. The mechanism of vision involves cis-trans photoisomerization of 11 -civ-retinal, an aldehyde formed from a linear polyene. Moreover, this kind of molecule exhibits high linear and non-linear electrical and optical properties. Short polyenes are also involved in pericyclic reactions, one of the most important classes of organic reactions. 

The connection between the optical properties and technological applications of macromolecules has been a subject of intense research and development for many years [1-5]. There is presently an emphasis on using materials and molecular architectures based on a very small size scale of less than 100s of nanometers [6-10], Revolutionary ideas and concepts have emerged which may lead to the creation of superior miniature size materials for a variety of applications. Some of these concepts are directed at synthetic schemes to recreate... 

While the linear absorption and nonlinear optical properties of certain dendrimer nanocomposites have evolved substantially and show strong potential for future applications, the physical processes governing the emission properties in these systems is a subject of recent high interest. It is still not completely understood how emission in metal nanocomposites originates and how this relates to their (CW) optical spectra. As stated above, the emission properties in bulk metals are very weak. However, there are some processes associated with a small particle size (such as local field enhancement [108], surface effects [29], quantum confinement [109]) which could lead in general to the enhancement of the fluorescence efficiency as compared to bulk metal and make the fluorescence signal well detectable [110, 111]. 

The electronic structure of fluorenes and the development of their linear and nonlinear optical structure-property relationships have been the subject of intense investigation [20-22,25,30,31]. Important parameters that determine optical properties of the molecules are the magnitude and alignment of the electronic transition dipole moments [30,31]. These parameters can be obtained from ESA and absorption anisotropy spectra [32,33] using the same pump-probe laser techniques described above (see Fig. 9). A comprehensive theoretical analysis of a two beam (piunp and probe) laser experiment was performed [34], where a general case of induced saturated absorption anisotropy was considered. From this work, measurement of the absorption anisotropy of molecules in an isotropic ensemble facilitates the determination of the angle between the So Si (pump) and Si S (probe) transitions. The excited state absorption anisotropy, rabs> is expressed as [13] ... 

Optical properties of solids encompasses a field of study too extensive to be covered adequately in a single volume. Monographs that emphasize different aspects of the subject, together with the topics they treat especially well, are listed below. 

Bulk matter, rather than particles, is the subject of Part 2. In Chapter 9 we discuss classical theories of optical properties based on idealized models. Such models rarely conform strictly to reality, however, so Chapter 10 presents measurements for three representative materials over a wide range of frequencies, from radio to ultraviolet aluminum, a metal magnesium oxide, an insulator and water, a liquid. 

Of the morphological phenomena mentioned in the last few paragraphs, that of twinning is likely to be of most frequent value in identification problems, but all the phenomena are significant from the point of view of crystal structure and the relation between internal structure and growth characteristics. The subject of crystal morphology in relation to internal structure will not, however, be pursued further at present it will be taken up again in Chapters VII and VIII. For the present, we shall continue our consideration of the problem of the identification of microscopic crystals we pass oij to discuss crystal optics, the relation between optical properties and crystal shape and symmetry, and the determination of refractive indices and other optical characteristics under the microscope. 

Reflectance. The optical properties (reflectance) are not in accord with the chemical properties for these coal samples, and the maximum reflectance of the coals indicates that they are higher in rank than would be concluded from the chemical data alone. These discrepancies are not surprising since these coals are thermally metamorphosed and may not follow the normal coalifica-tion curve (8). For the subject samples, it was decided that chemical data did not suitably indicate rank or the degree of thermal metamorphism, particularly in those instances where the samples contained so much ash that they were not suitable for routine chemical tests. The maximum reflectance in oil of these coals ranges from 2.6% to 11.5% (Table I). The lower reflectance is similar to that encountered in some semianthracites and anthracites, whereas the upper reflectance is more nearly that of graphite or long term, high tern-... 

One purpose of this tutorial paper on optical characterization is to provide a brief introduction for chemists to the concepts and methods involved in studies of the nonlinear optical properties of molecules and materials. The intent is to familiarize chemists with the range of commonly used techniques and their physical basis. An attempt is made to provide some background on macroscopic nonlinear optics, relating to what is actually measured, and the connection to molecular nonlinear optical properties. This paper is not intended to be a detailed or comprehensive review. The reader is referred to introductory (1, 2) and advanced (3-6) texts on nonlinear optics for more detailed or complete coverage of the subject. 

The present Volume 84 of Structure and Bonding is entitled "Metal Complexes with Tetrapyrrole Ligands III" and completes a series of three volumes dedicated to this general topic which started with Volume 64 and continued with Volume 74. The first volume contained topics such as stereochemistry of metal lotetrapyrroles, infrared and Raman spectra, biomimetic porphyrins, or metal loporphyrins with metal-carbon single bonds and metal-metal bonds. In the second volume, subjects like extended X-ray absorption fine structure or metal tetrapyrroles with special electrical and optical properties were covered. 

Metal nanoparticles have extraordinary size-dependent optical properties, not present in the bulk metal and have, consequently, been the subject of intense research during the past decade or so.27 Attention has recently focused on functionalising colloidal nanoparticles with molecular recognition components for potential sensing applications.28,29,30 We have prepared a new amido-disulfide functionalised zinc metalloporphyrin (8) which was self-assembled on to gold nanoparticles to produce a novel anion-selective optical sensing system (9) (Scheme 3).4... 

In the previous sections, theories were reviewed where the optical properties of polymer liquids were cast in terms of the microscopic properties of the constituent chains. The dynamics of polymer chains subject to external fields that orient and distort these complex liquids are considered in this section for a variety of systems ranging from dilute solutions to melts. Detailed descriptions of theories for the dynamics and structure of polymer fluids subject to flow are found in a number of books, including those by Bird et al. [62], Doi and Edwards [63], and Larson [64],... 

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