Differential polarization light scattering

However, (8.25) is not restricted to spheres but holds for particles of arbitrary shape. Thus, circular dichroism in particulate media includes a component that is the result of differential scattering, in contrast with circular dichroism in homogeneous media, which arises solely from differential absorption of left-circularly and right-circularly polarized light. 

Electron microscopy (5,40,52,63, 64), on the other hand, can provide direct information on the domain structure under favorable conditions, such as when the domains are crystalline. When the samples exhibit a semicrystalline superstructure, small-angle light scattering and polarized microscopy have been used in addition to electron microscopy to study the spherulitic structure. These methods are complemented by differential scanning calorimetry, and various techniques for studying dynamic mechanical behavior which can be interpreted to give additional, if somewhat less direct, information on domain structure. 

The thin sections were examined with the polarizing microscope, infrared spectroscopy, laser light scattering, differential scanning calo-... 

A. D. Buckingham and R. E. Raab. Electric field induced differential scattering of right and left circularly polarized light. Proc. Roy. Soc. (London), A, 345 365-377 (1975). 

Raman Optical Activity The Raman optical activity (ROA) effect is the differential scattering of left- or right-circularly polarized light by a chiral substrate where chirality is studied through Raman spectroscopy. 

Figure 42. Differential scatter of left and right circularly polarized light by poly-L-glutamic acid particles. Curve a, mean residue rotation of PGA reference state plotted on right-hand ordinate. Curve b, contribution of differential scatter term only, (Asi. —Asr) 3300/Cl. Curve c, total change in mean residue ellipticity due to differential scatter, includes differential scatter component of the (Aol— 4or) term. Curve d, comparison of empirical lO " values with total differential scatter. Curve e, approxima-...

The Rayleigh-Debye-Gans differential scattering cross section in the scattering plane for vertically polarized light (Eigure 14.1) is... 

Table II, Quantities for Calculating the Differential Scatter of Left and Right Circularly Polarized Light... 

Fig. 10. The calculated contribution of the differential scatter of left and right circularly polarized light, A[6]2>s, to the experimental ellipticity curve of a PGA suspension which exhibits an absorption due to light scattering of 0.16 to 0.20 absorption units in the 240- to 190-m/i wavelength range. This curve is due to the third term (/igL 1 ( ) 1...

This work demonstrated (a) that there are distortions in the CD of particulate systems (this had not previously been appreciated and the distorted spectra had been interpreted in terms of unique conformational features), (b) that the distorted spectra can be calculated and hence corrected, and (c) that there is a measurable differential scatter of left and right circularly polarized light by optically active particles. Thus, in addition to correcting spectra for suspensions of particulate systems that may be interpreted in terms of biomolecular conformation, the third point makes it possible to obtain an optical rotatory dispersion spectrum for the particle surface. In the case of membranes this will allow determination of relative amounts of surface area which are covered by ordered protein. This information coupled with the CD spectrum for the whole membrane will provide considerable information on the structure of membranes. 

Although the usual absorption and scattering spectroscopies cannot distinguish enantiomers, certain techniques are sensitive to optical activity in chiral molecules. These include optical rotatory dispersion (ORD), the rotation by the sample of the plane of linearly polarized light, used in simple polarimeters and circular dichroism (CD), the differential absorption of circularly polarized light. 

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