Scattering pole resonances: Relation to external and internal surface waves

The resonance scattering theory and the singularity expansion method are based on the complex‐frequency poles of the scattering amplitude; these are located off the real‐frequency axis and lead to prominent resonances. Their physical origin lies in a phase matching of surface waves generated on the scattering object; hence a study of the resonances will lead to information on these surface waves. This will be demonstrated here for immersed elastic objects of plane, spherical, and cylindrical geometry where even the physical nature (fluidborne or elastic type) of the surface waves can be identified along portions of their dispersion curves, and where for multilayered structures individual‐layer resonances can be distinguished, leading to solutions of the corresponding inverse problem.