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Static Light Scattering (SLS)

In contrast to dynamic light scattering (DLS) in static light scattering (SLS) time averaged scattering intensities are detected and observed at one specific scattering angle. One has to consider that colloids, from which the incident laser beam is scattered are no point scatterer. Their scattering pattern depends on their shape and size. If primary light waves are scattered on several scattering centers the resulting secondary waves differ in their path lengths. This difference of the path lengths results into a phase factor difference of the scattered light waves. Because of a strong relation between the phases of the scattered waves there is interference. Up to a specific size having the same range as the scattered light wavelength colloids are not point scatterer anymore. So one has to consider the interference of the scattered light resulting from scattering centers of different colloids as well as scattered intensities for a single large particle in the presence of intraparticle interference. From there the scattering ability of a colloid depends on the scattering angle where scattering light is detected. This leads to the particle form factor P(q). With increasing concentration of the colloidal dispersion one can obtain information about the static structure factor S(q) from the time averaged  intensities. The structure factor represents the structural arrangement of the particles and is determined by the particle interactions.

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