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

Paul G. AppleyardNigel DaviesCranfield UniversityDepartment of Environmental and OrdnanceSystemsRoyal Military College of ScienceShrivenham, Wiltshire, United Kingdom,SN6 8LAAbstract. IR extinction cross sections and mass extinction coefficientsof micrometer-sized particles of a variety of polar or partly polar insula-tors and semiconductors are calculated using several single-particleelectromagnetic scattering models including the well-established Mietheory for homogeneous spheres and more modern techniques such asthe Tmatrix method. The range of scattering models employed enable adetailed investigation of the impact of particle morphology on IR extinc-tion. Aerosol chamber measurements of the mass extinction coefficientsof a selection of particulate materials are also made and compared withthe theoretical calculations. Distinct extinction characteristics in the mid-and far-IR corresponding to reststrahlen band dispersions in the opticalconstants were predicted and observed. The results indicate the poten-tial limitations of this class of material as military IR obscurants.