Practical upper limits of the optical extinction coefficients of aerosols.

The optical extinction coefficients of some common spherical-particle aerosols are compared to practical upper limits estimated from the Mie theory for the visible and ir wavelength regions. Equations are developed to relate required refractive indices of aerosol materials to wavelength, particle size, and other parameters, so that the practical upper limit of the extinction coefficient is obtained. Some common aerosols, e.g., phosphorus smoke and sulfuric acid mists, are found to give extinction coefficients approaching the practical limit in the far ir (8-13 microm).