Information content of extinction and scattered-light measurements for the determination of the size distribution of scattering particles.

In the absence of information on the size distribution, the behavior of the refractive index within the particles, the shape and orientation of the particles, the nonlinear Fredholm integral equation of the first kind has to be replaced by a system of integral equations. These provide a solution for the kernel of the integral equation and for the desired function of the size distribution. This task has thus far not been tackled. The present study is, as a first step, concerned with the calculation of the optical properties of lognormally distributed particle collections as a function of the parameters that are typical for the distribution, i.e., gamma(0.5) (median value of the distribution) and sigma (standard deviation of the logarithms of the particle radii). The optical properties in their dependence on gamma(0.5) and sigma can be divided into three groups: (1) no dependence on gamma(0.5) and sigma; (2) a dependence on the median value of the distribution gamma(0.5); (3) optical characteristics are a function of gamma(o.5) and sigma. The calculations were based upon the refractive index m = 1.5. The dependence of the optical parameters on the refractive index is discussed.