SCATTERING CROSS-SECTION FOR TWO SPHERES

The total scattering cross-section for two neighbouring spheres is derived in terms of an infinite series of the ‘multiple’ scattering coefficients. The result broadly separates into two parts, one corresponding to a primary field, and the other to a secondary field or interference effects. Numerical results presented for Rayleigh particles (x > 1) indicate that for fixed parameter size x, fixed angle of incidence α and fixed separation constant δ, the ratio of the multiple scattering cross-section for two spheres to that of the single sphere cross-section remains approximately constant for varying refractive index m0. Comparison of the exact total scattering coefficient averaged over all orientations (i.e. a) is made with the approximate Rayleigh–Gans theory.