Theoretical Investigations on the Light Scattering of Colloidal Spheres. X. ``Scattering Ratio'' and Depolarization of Light Scattered at an Angle of Observation of 90°

The scattering ratio σ for nonabsorbing spheres and for an angle of observation γ of 90° is calculated from data given in the preceding publication [J. Chem. Phys. 34, 960 (1961), Paper IX, this issue], for m=1.05 (0.05) 1.30 and α=0.2 (0.2) 25.6. The scattering ratio represents the ratio of the total intensities scattered from a linearly polarized incident beam vibrating once parallel and, subsequently, perpendicular to the plane of observation. In the present instance of spheres, the results are identical with the depolarization in infinitely dilute systems. The experimentally attractive features of σ measurements are pointed out and the precautions to be observed for useful application of the theoretical data are enumerated. The periodicities in the σ (α) curves due to the primary, secondary, and tertiary undulations in the basic i(α) functions are briefly discussed with particular emphasis upon selecting conditions of optimum sensitivity of the method for particle size determinations, characterized by an error of not more than 1–3 A in particle diameter in monodisperse systems.