Indexing the scatterers

The sample contains a large number of scattering centres belonging to various species. Let us rewrite (7.2.1) with the following notation. We use the index ( = 1,. . . , (V) to mark a molecule, the index i(i = 1,. . . Na) to mark a monomer on a molecule a made up of Na links (Na monomers), and the index 

In Chapter 6, we defined the centres which scatter neutrons or photons as being (respectively) nuclei or electrons. In this chapter, the set of all the centres belonging to a monomer will be considered as a unique scattering centre. This more economical definition is justified by the fact that, in the interval (0, qm ) where we study the behaviour of scattering cross-sections, the length q x is always large as compared to atomic distances. Let rai be the position vector of the centre of mass of monomer i. Then, suppose 

The expression of the cross-section per unit volume becomes (for q jmax)  

This notation is very general but it does not take into account the fact that a large number of molecules may be of the same kind. For instance, the molecules of solvent are practically identical, and the same is true for sets of molecules constituting the solute. By taking this fact into account, it will be possible to group certain terms of the preceding equation. 

let be the set of all the molecules that are able to scatter the radiation and let s/,38,.. . be subsets of S for instance, si = 0 is the set of the molecules of solvent. To indicate that a molecule belongs to si, we shall simply write (in a 

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Relative refractive index. The scattering efficiency of a particle increases as the contrast in refractive index between the particle and the surrounding liquid increases. Emulsion lightness, therefore, is high when the refractive index of the droplets is either much smaller or much greater than the refractive index of the... 

Due to the rhombic shape of the unit cell, it should also be possible to index the scattering pattern of the C0I2 phase on the basis of the plane crystallographic group cm. However, as the group cm possess mirror planes this would not be conform to the chirality of the molecules. 

The physics of X-ray refraction are analogous to the well known refraction of light by optical lenses and prisms, governed by Snell s law. The special feature is the deflection at very small angles of few minutes of arc, as the refractive index of X-rays in matter is nearly one. Due to the density differences at inner surfaces most of the incident X-rays are deflected [1]. As the scattered intensity of refraction is proportional to the specific surface of a sample, a reference standard gives a quantitative measure for analytical determinations. 

If the scattering particles are in a dielectric solvent medium with solvent refractive index Uq, we can define the excess... 

One of the characteristics of the porous film is that there is no effect on the film size in the solvents, despite the existence of PVAc, because of the enormous space taken up by the PVA cells versus the PVAc amount. If the porous film is dipped in a solvent, the PVAc concentration in the PVA cells may be appreciated by the residual PVAc amount. Because the refractive index of the PVAc solution in contact with PVA cells becomes lower as the amount of PVAc with a low-refractive index increases, the wavelength of the transmitted light for the porous film shifts to the short side, and the color of the scattered light shifts to the yellow side. This consideration successfully explains the experimental results in Table 4. 

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