Forced Rayleigh scattering method

The force Rayleigh scattering method was developed by Nagashima s group. Thermal diffusivity can be measured in a contact-free manner within a time interval of 1 ms, with a small temperature rise of 0.1 K and with a small volinne of about 10 mm The sample needs to be colored by an admixture of a dye for suitable absorption of a heating laser beam. The principle is schematically shown in Fig. 32. Two beams of equal intensity divided by means of abeam splitter cross in the sample to create... 

Figure 32. Schematic diagram of the forced Rayleigh scattering method. (Reprinted from Ref 175 with permission of the American Institute of Physics.)...

Similar to the thermal lensing method, the thermal diffusion forced Rayleigh scattering method is intrinsically differential, and it also induces an unavoidable free convection effect. Compared to other methods, the setup used in this method is complicated. 

Experimental Methods of Thermophoresis in Liquids, Fig. 3 Thermal diffusion forced Rayleigh scattering setup. BS is the beam splitter, and DPC is the double Pockels cell used to change the incident... 

In recent years, in addition to theoretical developments, e.g., reptationW and tube theories,(i3,i4) iYiqyq have been many new analytical techniques,5) such as electron-induced X-ray fluorescence, the NMR field gradient method, forced Rayleigh scattering (FRS), forward recoil spectrometry (FRES), photon correlation spectroscopy, Rutherford back scattering. 

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). 

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. 

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