Form birefringence and dichroism

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

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... 

From the above expressions, the form birefringence and dichioism can be calculated. The form dichroism, in particular, has the simple interpretation of being the anisotropy in the second-moment tensor of the structure factor. It is also evident that the form dichroism appears at a higher order in the wave number than the form birefringence. 

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,... 

Birefringence and dichroism represent two optical methods which can be applied to materials under flow conditions, forming the basis of Optical Rheometry [3,4]. The aim of these two techniques is to measure the anisotropy of the complex refractive index tensor n = n - i n". Birefringence is related to the anisotropy of the real part, whereas dichroism deals with the imaginary part. Recent applications of birefringence measurements to polymer melts can be foimd in Chapter III.l of the present book. 

The study of the birefringence of the Kraton single crystal and of the effect of stress applied along and perpendicular to the extrusion directfon has shown that the birefringence is entirely due to form birefringence and that the di ersed styrene phase and the butadiene matrix consist of randomly oriented chains Thisresults have been confirmed by infra-red dichroism studies ... 

Efimova Al et al (2007a) Effect of form anisotropy of silicon nanocrystals on birefringence and dichroism in porous silicon. Phys Stat Sol (c) 4(6) 1991-1995... 

This is the form of the scattering matrix for any medium with rotational symmetry even if all the particles are not identical in shape and composition. A collection of optically active spheres is perhaps the simplest example of a particulate medium which is symmetric under all rotations but not under reflection. Mirror asymmetry in a collection of randomly oriented particles can arise either from the shape of the particles (corkscrews, for example) or from optical activity (circular birefringence and circular dichroism). 

Analogous to the definitions of linear birefringence and linear dichroism following equations (2.15) and (2.21), the form of equation (2.30) suggests the following optical anisotropies for circularly polarized light ... 

The Optical Theorem Form Dichroism and Birefringence From Dilute Suspensions 71... 

As to infrared spectroscopy - and the same holds good for other spectral ranges -the orientational order is readily observable in form of dichroism Being related to the molecular shape, the molecular polarizability is anisotropic as well. By the alignment of the molecules this anisotropy is transferred to the sample, however damped due to the imperfect order as described by the order parameters. As a consequence, the dielectric function and furthermore the (complex) refractive index are anisotropic, so that eventually (linear) dichroism and birefringence occur. 

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