Structural resonances in a coated sphere: investigation of the volume-averaged source function and resonance positions.

Morphology-dependent resonances in a coated sphere are investigated by computation of the volumeaveraged source function obtained from Lorenz-Mie theory. Analytic expressions for the source function in absorbing and nonabsorbing spheres are given in a suitable form for computations. An advantage of the investigation of the source function is that core and shell contributions can be computed and examined independently. Furthermore the influences of the refractive index and the thickness of the outer layer on resonance positions and height are studied in detail. These influences are presented for the α(104) partial-wave example.