Optical characterization of powders: the use of Mie theory and composite media models

The measurement of the optical response of materials occurring as finely divided powders is difficult due to the complex interaction of the optical wave with the material. Guided by methods used to study the optical properties of composite media, we have developed experimental and theoretical techniques for characterizing the optical properties of powders. We have applied these techniques to two supported catalysts and have observed several optical effects arising from the very small particle size of these materials.