Polarization and depolarization

If all the molecules are oriented in the same direction, for example, parallel to the z axis, then p is clearly equal to unity. If the molecules are partially oriented, p 1-For p 1, we call p fluorescence depolarization. 

Depolarization is a manifestation of the intrinsic properties of the macromolecule. It is the result of Brownian motion and it involves the translation of molecules and their rotational movements. Since Brownian motion is affected by temperature, solvent viscosity, and the size and shape of the molecule, these factors also affect the value of p. The angle 0 between the original direction of the molecules in a 

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An important experimental quantity for studying molecular interactions in gases and liquids is the scattering of laser light. When polarized light is scattered by a fluid, both polarized and depolarized components are produced. The depolarized spectrum is several orders of magnitude less intense than the polarized spectrum and much more difficult to observe. A great deal of information has been obtained about molecular motions from such spectral analyses. 

To perform structural research on a food stuff into which a colorant is incorporated, special properties of fluorescing molecules are exploited fluorescence efficiency, fluorescence lifetime, fluorescence quenching, radiationless energy (Foerster) transfer, stationary or time-dependent fluorescence polarization and depolarization." Generally, if food colorants fluoresce, they allow very sensitive investigations which in most cases cannot be surpassed by other methods. 

Typically, nonisothermal relaxation is effectively employed in the studies of thermally stimulated luminescence (TSL), condnctivity (TSC), polarization, and depolarization. 

It is also necessary to note that the success of TSR techniques to obtain information on trapping states in the gap depends on whether or not the experiment can be performed under conditions that justify equation (1.2) to be reduced to simple expressions for the kinetic process. Usually, the kinetic theory of TSR phenomena in bulk semiconductors—such as thermoluminescence, thermally stimulated current, polarization, and depolarization— has been interpreted by simple kinetic equations that were arrived at for reasons of mathematical simplicity only and that had no justified physical basis. The hope was to determine the most important parameters of traps— namely, the activation energies, thermal release probabilities, and capture cross section— by fitting experimental cnrves to those oversimplified kinetic descriptions. The success of such an approach seems to be only marginal. This situation changed after it was reahzed that TSR experiments can indeed be performed under conditions that justify the use of simple theoretical approaches for the determination of trapping parameters ... 

Single-bilayer DODAC (6) vesicles Magnetite particles prepared in situ in vesicles from Fe2+/Fe3+ and OH" Static and dynamic polarized and depolarized light scattering and static and time-resolved dichroic anisotropy, as well as conventional magnetization vs applied magnetic field determinations were used for characterization 794... 

Figure 10.12 Polarized (parallel polarizers) and depolarized (crossed polarizers) spectra of undeformed polyisobutylene at room temperature.

The depolarization behavior is derived in the same way (Appendix 2). Figure 47 shows both the polarization and depolarization transients of a blocking experiment on PbO (orh.) characterized by consistent diffusion values. As already stated, only... 

In contrast to the atomic and ionic polarization processes, the diffusional polarization and depolarization processes are relatively slow and strongly temperature dependent. Temperature-activated diffusional polarization processes also occur in ionic crystals and can involve ionic migration and changes in the orientation of defect complexes. 

For monodisperse systems the normalized polarized and depolarized time correlation functions can be expressed as (7)... 

According to Table 4-3, the former should exhibit two v(PtCl) (Ai(p) and E(dp)) and two v(PtBr) (A p) and E dp)) both in IR and in Raman spectra. Here, p and dp denote polarized and depolarized vibrations, respectively. This was found to be the case (trace 3a of Fig. 4-3). In contrast, the latter should exhibit three v(PtCl) 2A p) and B (dp)) and three v(PtBr) (2A (p) and Biidp)) both in IR and in Raman spectra. Trace 3b of Fig. 4-3 shows that two polarized bands of /li-type are observed for each vibration because fi-type vibrations are weaker than 4-type vibrations. Thus, comparison of Raman spectra of the two isomers should be made using 4-type (polarized) vibrations. 

In Ref. (163) the techniques introduced above were illustrated for He-He and He-H2 collisional complexes. In Refs. (316,317) the property functions were applied in full quantum-statistical calculations of the dielectric second virial coefficient and of the polarized and depolarized Raman spectrum of the He gas. Some further applications were reported by Rizzo and collaborators318- 322. 

Moszynski R, Heijmen TGA, Wormer PES, Van der Avoird A (1996) Ab initio collision-induced polarizability, polarized and depolarized Raman spectra, and second dielectric virial coefficient of the helium diatom. J Chem Phys 104 6997-7007... 

Proffitt M, Frommhold L (1980) The collision-induced polarized and depolarized raman spectra of heliumand the diatompolarizability. J Chem Phys 72 1377-1384... 

A remedy obviously should be available using polarization tricks. In conventional Raman spectroscopy, the isotropic and anisotropic components are deduced from linear combinations of the polarized and depolarized spectra, while a nonresonant part is not clearly recognized (41). In frequency-domain CARS it is known how to suppress the nonresonant contribution and solely measure resonant scattering (isotropic plus anisotropic part) (42). In time-domain CARS, polarization interference can do an even better job with three magic cases (derived in Refs. 35,39). These authors derived explicit expressions for the coupling factors F in Equations (2)-(4) ... 

Here p and dp refer to polarized and depolarized, respectively. Data taken from (4). Assignments are not based on normal coordinate analysis and are made on the basis of polarizations and by analogy with the IR data. 

Figure 2.7-4 Examples of tetra-atomic molecules belonging to different point groups. They can be distinguished by the number of polarized and depolarized Raman active vibrations, the infrared active vibrations and the coincidences of the frequencies of infrared and Raman active bands.

In the present study, an instmment has been established for polarized and depolarized Raman scattering measurement of supercritical fluid along its isotherm to realize the investigations stated above. Preliminary results for supercritical CF3H are given to draw a schematic picture of the dynamics. 

M. H. Proffitt and L. Frommhold. Collision induced polarized and depolarized Raman spectra of helium and the diatom polarizability. J. Chem. Phys., 72 1377-1384 (1980). 

H. C. Lucas, D. A. Jackson, J. G. Powles, and B. Simic-Glavaski. Temperature variation of polarized and depolarized scattered light spectra from liquid benzene derivatives. Molec. Phys., 75 505-521 (1970). 

Appraisals of the optical properties of lipid solutions and dispersions will provide information on concentrations, aggregation and stability, phase transitions, densities, and repeating structuresJ Measurements of refractive index, scattered light intensity (polarized and depolarized), and birefringence are relatively easy laboratory methods on which certain product specifications may be based. Also, fluorescent techniques can readily provide information on lipid movements and transfer of lipid between particles. ... 

Although the exact biochemical mechanism of toxicity has not been identified for toluene, it is known that the primary toxic effect of toluene is dysfunction of the brain and central nervous system (CNS-nar-cosis). The main function of neurons is to conduct electrochemical signals to one, several, or thousands of other cells. The normal physiology of these neurons is, in turn, largely dependent on the integrity of the cell membrane, which polarizes and depolarizes during the transmission of these signals. Thus, the most probable mechanism of toxicity is the unique... 

The scattering cross section may be divided into two parts, polarized and depolarized. Experimentally, the most common polarizations used in the study of molten salts and other isotropic liquids and glasses are those denoted as... 

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