Forced Rayleigh light scattering

Experimental evidence was obtained showing that DT itself may be temperature dependent [109]. Another method to determine DT is the measurement of thermodiffusion in polymer solutions by forced Rayleigh light scattering [213]. This technique has the advantage that the employed temperature gradients are very small so that the coefficients are determined close to thermal equilibrium. 

Leger L, Hervet H, Rondelez F (1981) Reptation in entangled polymer solutions by forced Rayleigh light scattering. Macromolecules 14 1732-1738... 

Phase Analysis Light Scattering and Forced Rayleigh Light Scattering... 

R. G. Horn, ""Refractive indices and order parameters of two liquit crystals, J. Phys., vol. 39, pp. 105-109, 1978 W. Urbach, H Hervet, and F. Rondelez, ""Thermal diffusivity measurement in ne matic and smectic phases by forced Rayleigh light scattering, Mo lec. Cryst. Liq. Cryst., vol. 46. pp. 209-221, 1978. 

H. Deschamps and L. Leger. Self-diffusion measurements in polymer solutions at the temperature by forced Rayleigh light scattering. Macromolecules, 19 (1986), 2760-2765. 

L. L6ger, H. Hervet, and F. Rondelez, Reptation in Entangled Polymer Solutions by Forced Rayleigh Light Scattering , Macromolecules 14,1981, pp 1732-1738. 

The nature of polymer motion in semidilute and concentrated solutions remains a major question of macromolecular science. Extant models describe polymer dynamics very differently 3-11). Many experimental methods have been used to study polymer dynamics (12). One meAod is probe diffusion, in which inferences about polymer dynamics are made by observing the motions of dilute mesoscopic probe particles diffusing in the polymer solution of interest. Probe diffusion can be observed by several experimental techniques, for example, quasi-elastic light scattering spectroscopy (QELSS), fluorescence recovery after photobleaching (FRAP), and forced Rayleigh scattering (FRS). 

In the forced Rayleigh scattering technique, the diffraction lattice of the excited state is formed by the interference of the two laser fluxes. A probe laser then follows the disappearing process of this lattice [21], The disappearance process of this lattice reflects the lifetime of the excited state T and molecular diffiision D. A plane wave laser light with a wavelength X is divided into two and they cross each other at an angle q to observe the interference pattern with a period A. In the constructive interference area, the probe will be excited and the striation of the excited state can be observed. Period A of the striation is expressed as... 

T. Chang, C. C. Han, L. M. Wheeler, and T. P. Lodge. Comparison of diffusion coefficients in ternary polymer solutions measured by dynamic light scattering and forced Rayleigh scattering. Macromolecules, 21 (1988), 1870-1872. 

A light beam propagating in matter interacts with the electrons of the medium. In insulators, the electrons are bound and the incident radiation induces a local polarization. Therefore, a scattering centre is a small polarizable element with the size of a monomer this element can be assimilated to a dipole in forced oscillation regime. The radiation produced by this dipole is the scattered radiation. This is Rayleigh scattering. 

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