Abstract

Scattering of light by a single-layered sphere is investigated in the limit of a tiny core. It is shown that the first-order correction to Mie scattering due to the presence of the core is a modified Rayleigh term determined by an incident wave which is the internal field of a homogeneous sphere with the parameters of the shell. Assuming the shell is nonabsorbing, the absorption cross section for the composite particle is calculated and applied to the case of absorption of visible light (λ = 0.5 μm) by a water droplet containing a tiny graphitic carbon (soot) core. Results for absorption cross section per unit volume of soot vs radius of the water droplet predict oscillations which may be identified with resonances in the internal field of the nonabsorbing water droplet, corresponding to the electric dipole mode (n = 1). The mean value in the region of oscillations is around 23 m²/cm³ which is to be compared with a maximum value of 13 m²/cm³ in a polydispersion of carbon particles in air.

© 1985 Optical Society of America