Approximate two-parameter phase function for light scattering

A two-parameter phase function is described for highly anisotropic angular scattering distributions. The phase function has a convenient analytic representation since it is the generating function for the Gegenbauer (or ultraspherical) polynomials. Sample calculations illustrate the large variety of forward-to-backward scattering amplitudes and shapes that can be fit with the two parameters. Illustrative phase functions are given that approximate light scattering distributions predicted for several biological and atmospheric specimens from Rayleigh-Gans and Mie models. A suggested classification scheme for size and refractive index of microparticles in human blood is presented as a potential application of the phase function with two parameters.