Force Rayleigh scattering , probe

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). 

Probing of mobilities in multilameUar vesicles by forced Rayleigh scattering... 

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... 

Forced Rayleigh scattering [16] has been used to probe the dynamics of a conducting polymer, poly(3-octylthiophene), in solution. The optical labels which lead to the transient grating are the photoexcited states on the chains... 

Forced Rayleigh scattering and fluorescence photo-bleaching recovery also belong to the family of probe-diffiision techniques, but they are based on a quite different principle to observe the seU-diflusion of particles by their Brownian motions. Interested readers are advised to learn the details from the literature. 

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