where δ = α/(zν) = 0.06 is a critical exponent. All these relationships are of essential importance for fitting the scaling function according to Bhattacharjee and Ferrell. It should be emphasized once more that the complete theoretical framework can be found in [15], [16], [17], [18] and [19], together with a successful application of the theory to experimental results in [23].
3.2 Light Scattering
Light scattering provides another way of investigating critical systems and testing theories of fluctuations. The theory of light scattering—or, more generally, the scattering of electromagnetic radiation by particles—is extensive and can be presented here only in abbreviated form. Its applications range from the investigation of intermolecular processes to the observation of biological macromolecules and living microorganisms. Scattering theory is not restricted to the electromagnetic spectrum: electrons, neutrons and even whole atoms can be scattered by crystal structures or fluids, and the resulting scattering behaviour can reveal important physical and chemical properties of the object or system under investigation. More detailed introductions to these fields are provided in [46], [47] and [48].
3.2.1 Electromagnetic Scattering Theory
The basic arrangement of a scattering experiment is shown in Fig. 3.2. In principle, the polarization plane of the incident light can be varied. This is of little use in the present work, however, because the molecules are isotropically polarizable. To describe the scattering geometry, it is customary to define the scattering vector q, namely the difference between the wave vector ke of the incident light and the vector ks directed from the scattering centre towards the detector:
The scattering vector is thus a measure of the momentum transferred in the scattering event.
We must now ask which quantities couple the emitted electromagnetic wave to the system under investigation and what information can be obtained from that interaction.
Original mathematical typography retained. .