Calculation and measurement of infrared mass extinction coefficients of selected ionic and partially ionic insulators and semiconductors: a guide for infrared obscuration applications

IR extinction cross sections and mass extinction coefficients of micrometer-sized particles of a variety of polar or partly polar insulators and semiconductors are calculated using several single-particle electromagnetic scattering models including the well-established Mie theory for homogeneous spheres and more modern techniques such as the T matrix method. The range of scattering models employed enable a detailed investigation of the impact of particle morphology on IR extinction. Aerosol chamber measurements of the mass extinction coefficients of a selection of particulate materials are also made and compared with the theoretical calculations. Distinct extinction characteristics in the mid-and far-IR corresponding to reststrahlen band dispersions in the optical constants were predicted and observed. The results indicate the potential limitations of this class of material as military IR obscurants. (C) 2004 Society of Photo-Optical Instrumentation Engineers.