Birefringence and Dichroism

The phenomenon of birefringence is the one of most importance to rheo-optics and is introduced in this section. Section 9.3 on polarization of light, explains the primary methods for measuring birefringence. Dichroism, although in fact an absorption process, is very closely coupled to birefringence and therefore is also defined here. 

Examples of molecules possessing (a) isotropic polarizability and (b) anisotropic polarizability. 

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Constantine S, Zhou Y, Morals J and Ziegler L D 1997 Dispersed optical heterodyne birefringence and dichroism of transparent liquids J. Phys. Chem. A 101 5456-62... 

Ruch F. Birefringence and dichroism of cells and tissues, in Physical Techniques in Biological Research, Vol. Ill, Part A (Pollister AW, ed.), Academic Press, New York, 1966, pp. 57-86. 

The dielectric tensor describes the linear response of a material to an electric field. In many experiments, and particularly in optical rheometry, anisotropy in is the object of measurement. This anisotropy is manifested as birefringence and dichroism, two quantities that will be discussed in detail in Chapter 2. The nonlinear terms are responsible for such effects as second harmonic generation, electro-optic activity, and frequency tripling. These phenomena occur when certain criteria are met in the material properties, and at high values of field strength. 

If the birefringence and dichroism are coaxial, (0 = 0"), this material is described by equation (2.25) with the Jones matrix rotated by an angle 0. ... 

The scattering of light from a suspension of particles will cause the light transmitted through such a material to be changed in phase and amplitude. If particles are nonspheri-cal, and have a net orientation, a birefringence and dichroism will result. 

The Onuki-Doi Theory of Form Birefringence and Dichroism 75 which, when compared with (4.83), gives the result that... 

Evidently, Raman scattered light contains information about both the second and the fourth moments of the orientation distribution function. This is in contrast to birefringence and dichroism measurements, which respond only to anisotropies in the second moments. 

In section 4.7, the Onuki-Doi theory for form birefringence and dichroism was developed and presented in equations (4.91) and (4.92). It is left to calculate the structure factor, S (q), as a function of flow. This was done in the limit of weak oscillatory flow for the... 

As noted in the figure, these designs can accommodate samples with coaxial birefringence and dichroism. It can be shown that the presence of coaxial birefringence will not appear in the measured signals. All of the designs produce signals of the form,... 

Figure 8.9 Optical train for the measurement of noncoaxial birefringence and dichroism.

The procedure to extract both the birefringence and dichroism would entail first using the intensity information from D1 to determine the retardadon and the angle 0. These values can then be used in the Fourier decomposition of the intensity from I2 to obtain 5" and 0". 

The integration of the optics within the stress rheometer allows the simultaneous acquisition of optical and mechanical properties of the sample, which can be important for determining the relationship between a material s microstructure and its rheological response. The particular rheometer used here has an open construction that easily accommodates the insertion of an optical train for the purpose of birefringence and dichroism measurements. The optical train consisted of a helium-neon light source with a (P/RII)/)(,G... 

The optical apparatus used in this study was designed according to the strategy described in section 8.4.3, which permits the simultaneous measurement of birefringence and dichroism. The source was a infrared diode laser that generates light at a wavelength in the... 

Figure 10.7 The relaxation of birefringence and dichroism following a step strain. The...

This composite material contains both linear and circular birefringence and dichroism. The orientation of the linear birefringence is at 0 and the orientation of the linear dichroism is at 9". 

A. Onuki and M. Doi, Flow birefringence and dichroism of polymers. I. General theory and application to the dilute case, J. Chem. Phys., 85,1190 (1986). 

Birefringence and dichroism in Physical techniques in biological research... 

As it is easily derived from Eqs. 6.4-18, the relations are valid also for birefringence and dichroism. As far as optical activity in the UV/VIS range is concerned transformations on this basis have already been widely used for decades to correlate circular-dichroism bands and Cotton effects, i.e. anomalies of the optical rotatory dispersion (Moffit and Moscowitz, 1959 Blout et al., 1967). Another relation is mentioned in the following section. 

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