Subject incoherent scattering

We shall assume, in addition to single scattering, that the particles are many and their separations random, which implies incoherent scattering. That is, there is no systematic relation among the phases of the waves scattered by the individual particles thus, the total irradiance scattered by the collection is just the sum of the irradiances scattered by the individual particles. Even, however, in a collection of randomly separated particles, the scattering is coherent in the forward direction, a subject to which we shall return in Chapter 3. 

Interesting results have been obtained by a combination of NMR and quasi-elastic incoherent neutron scattering. The presence of one single line in an NMR spectrum, for all the water concentrations, can be interpreted in two ways either we have only one kind of water molecule with a very well defined environment or we have different kinds subject to a fast chemical exchange (t < 10 3 sec.). Two regimes of absorption have been demonstrated and two different motions have been characterized both by NMR spin lattice relation time measurements and quasi-elastic incoherent neutron scattering. From these results and from results obtained on the Nafion salts W a structural model will be proposed (9). 

Of more importance for the elucidation of problems in molecular structure is the study of the phenomenon known as incoherent or Raman scattering. In order to understand the origin of this phenomenon, let us calculate the dipole moment for the transition a — 6 when the system is subjected to radiation of frequency v. The wave func-... 

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