Excess Rayleigh ratio

As will be demonstrated later, LS can be quantified by an experimental quantity termed the excess Rayleigh ratio between solution and solvent, R, which is related to the concentration and molecular weight of solute by the following expression... 

Note Several modifications of the Zimm plot are in frequent use the most common one uses the excess scattering instead of the excess Rayleigh ratio. 

R(0) is the excess Rayleigh ratio, n and are the refractive index of the solvent and the wavelength of the light source. 

From thermodynamic arguments, Ac2 is related to the chemical potential, jjj. Thus, the excess Rayleigh ratio may be written [9]... 

A continuous analog output is provided from the 90° sensor and all the sensors are sampled every 2 sec. The molecular weight range extends from 10 to 10 Daltons and the rms radii from 10 to 50 nm. The total cell volume appears to be about 3 pi and the scattering volume is 0.02 p t. The detector has a sensitivity, defined in terms of the minimum detectable excess Rayleigh ratio of 5 x 10 cm which is difficult to translate into normal concentration units but appears to be equivalent to a minimum detectable concentration of about 10 g/ml. 

When light passes through an inhomogeneous medium such as a polymer solution, it is scattered in all directions. The light scattering at an angle 6 by the solute is measured by the excess Rayleigh ratio Re which is defined by... 

Here the prime denotes the excess scattering from the liquid due to the solute n and rio are the refractive indices of the solution and solvent, respectively dn/dc is the specific refractive index increment with concentration c is the concentration of solute in mass per unit volume II is the osmotic jmessure of the solution, and the other terms are as described previously. Jig, commonly known as the excess Rayleigh ratio, is the difference between the Rayleigh ratios of the solution and the pure solvent ... 

The excess Rayleigh ratio Rg can be derived from the raw galvanometer readings Ig and Igg when the sample container contains die solution and the solvent, respectively, with the photocell of Fig. 4.11 positioned at an angle 9 in both cases. Hie equation used is... 

The values of excess Rayleigh ratio R g calculated from Eq. (4.77) using the above value of k and data of Table P4.17.1 are recorded in Table P4.17.2. 

Figure 3,21 Results from (a) dynamic light scattering DJD vs. volume fraction of droplets), and (b) static light scattering (excess Rayleigh ratio vs. volume fraction of droplets) measurements at the emulsification...

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