Alternatives to Mie Theory
Abstract
This report examines how the scattering properties of spheres can be calculated without using Mie theory. Specifically, the scheme of ray optics is used to develop software that calculates the phase matrix elements of polydisperse spheres in geometrical optics limit. (Ray optics works well for size parameters greater than 400, and becomes more accurate for particles containing significant absorption.) In addition, this report examines a collection of numerical algorithms, developed by Nussenzveig and Wiscombe, that use complex angular momentum theory to obtain the efficiency factors for Mie scattering. Although accurate for size parameters greater than 20, it is shown that these algorithms are only computationally efficient for size parameters greater than 500. Finally, this report establishes regions of validity for other approximations to the Mie efficiency factors which exist in the scientific literature. It is shown that existing approximations can give reasonable estimates for the extinction efficiency for most size parameters and complex indices of refraction. On the otherhand, the approximations for the absorption efficiency are much less accurate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1988
- Accession Number
- ADA206820
Entities
People
- David R. Longtin
- Eric P. Shettle