PARTICLE SHAPE AND STRUCTURE ANALYSIS FROM THE SPATIAL INTENSITY PATTERN OF SCATTERED LIGHT USING DIFFERENT MEASURING DEVICES

The spatial intensity pattern of scattered light from nonspherical particles was investigated numerically and experimentally in order to obtain—beside size—sensitive shape information. The discrete dipole approximation (DDA) was used to calculate the light scattering pattern for some basic types of particle shapes. From these calculations the lower size limit where shape information can successfully be detected from light scattering was found at a size parameter of approximately 1. It can be even lower if elongated particles (cylinders) are present. For the exemplary studies three different laboratory instruments available to the authors were utilized. The comparison of experimental and numerical results yielded good correlations, which confirmed the selected theoretical approach. Thus, it is possible to develop experimental setups for specific applications only on basis of theoretical data. From the experiments we found that azimuthal scattering at a constant scattering angle is a promising setup for shape characterization, which can be adapted to specific applications with high flexibility. For supermicron particles the surface structure also contributes to the scattering pattern provided the characteristic size of surface elements substantially exceeds the wavelength of the light source.