Rayleigh scattering, description

Next, we introduce the theory of Rayleigh scattering (Section 5.3), the first of many models covered in the chapter. The Rayleigh theory for dilute systems and solutions is developed here, with illustrative examples of the determination of molecular weight and the second virial coefficient. This is followed by a brief description of some of the basic experimental considerations and an introduction to absorbance and turbidity (Section 5.4). 

The following classical description [21], while failing to explain many of the quantitative aspects of the Raman effect, is able to capture its qualitative behavior and provides a useful basis for understanding this phenomena. As in the case of Rayleigh scattering theory, the source of the scattering is the oscillating dipole moment,... 

Fig. 8. (a) LIF signal intensity versus laser energy from the excited CH B-X fli(12) rind the excited CN B-X Pi,2(10) lines, (b) Calibration of the detection system by N2 Rayleigh scattering. Right side Schematic description of the Rayleigh scattering calibration procedure for the measurement of absolute CH radical concentration NcH Details are described in the text. 

Rayleigh first presented a description of light scattering and adsorption from small particles. The conditions for Rayleigh scattering are ... 

As it was noted in Chaps. 3 and 4 the dipole moment modulus and the polarizability tensor invariants practically do not change for the family of the most stable configurations [52]. We can expect, that the first-hyperpolarizability tensor invariants which are important for description of interaction-induced hyper-Rayleigh scattering, also change weakly for all most stable configurations. 

Rayleigh and Raman scattering are two-photon processes in which absorption of a photon is followed coherently by emission of the same and of a different photon, respectively. They are thus second-order processes if we use a description in which the interaction between matter and radiation is used as a perturbation. The complete second-order treatment (Sushchinskii, 1972 Behringer, 1974) is outside the scope of this contribution. We shall start with the simplified description of the scattering tensor that is familiar from many previous treatments. The scattering tensor describing the Raman transition from the molecular eigenstate / > to /> is represented by a 3 X 3 matrix with (molecule-fixed) Cartesian components (in atomic units, ft = 1)... 

In the nearest vicinity of the spinodal, concentration fluctuations become correlated, and it is necessary to pass from Rayleigh-Einstein s scattering to Rayleigh-Debye .s approximation for the correct description of light scattering. 

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