Near-Field Scattering Dynamics

y represents the square of the spatially averaged electric field of the scattered wave Es = ( r. Eg, E ) as a function R. The scattered field consists of all three components of the electric field vector, where the angular components. Eg and Ep are perpendicular to the particle surface and the radial component, Tr, lies normal to the surface. This provides a measure of the ability of the sphere to convert the incident electric field intensity to a near-field intensity. Qr is the main contribution of Qnf, approximately 67%, which is due to the radial field component only and provides a measure of the sphere s ability to convert the incident electric field into a radially directed field. Because the r field component increases proportionally to R Qjvf will increase faster than Qca, which is only proportional to RtK As R a, will approach the asymptotic value of Q.  

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Freedom to choose between absorption and near-field scattering dynamics... 

The use of photon correlation spectroscopy to study the dynamics of concentration fluctuations in polymer solutions and gels is now well established. In bulk polymers near the glass transition there will be slowly relaxing fluctuations in density and optical anisotropy which can also be studied by this technique. In this article we review the development of the field of photon correlation spectroscopy from bulk polymers. The theory of dynamic light scattering from pure liquids is presented and applied to polymers. The important experimented considerations involved in the collection and analysis of this type of data are discussed. Most of the article focuses on the dynamics of fluctuations near the glass transition in polymers. All the published work in this area is reviewed and the results are critically discussed. The current state of the field is summarized and many suggestions for further work are presented. 

Figure 3-6. Example of lattice dynamical calculations on ir-bonded tridimenional crystals with short range interactions. Dispersion curves for cubic diamond along the F — (K) —> X symmetry direction. Experimental points from neutron-scattering experiments dispersion curves from least squares frequency fitting of a six parameters short range valence force field (from [60]). The Raman active phonon is the triply degenerate state indicated with F j near 1300 cm Notice that at k 0 the degeneracy at F is removed because of the lowering of the symmetry throughout the whole BZ. Notice also the three acoustic branches for which v 0 at k F.

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