Perturbation approach for light scattering by an ensemble of irregular particles of arbitrary material.
The statistical version of a perturbation approach for light scattering by perfectly conducting irregular particles, presented in a recent paper [J. Opt. Soc. Am. A 6, 385-402 (1989)], is extended to arbitrary material. Analytical expressions for the second-order perturbational cross sections are presented for a randomly oriented particle ensemble. A comparison with results obtained from a numerically exact method is carried out to determine the range of validity of the perturbation results. For size parameter alpha < 7 (alpha identical with kR; k wavenumber and R = particle radius) and slightly absorbing material the agreement is very good only if the surface deviations from the reference sphere are much smaller than wavelength. Problems occur, however, for larger size parameters near sharp resonances in the case of nonabsorbing material. Generally, maximum errors arise for backscattering.
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